Credentials are not available unless the job is run as SYSTEM

### Version report

Jenkins and plugins versions report:

```
Jenkins: 2.263.3
OS: Linux - 3.10.0-1160.41.1.el7.x86_64
aws-credentials:1.30
credentials:2.5
credentials-binding:1.27
pipeline-aws:1.43
```

- What Operating System are you using (both controller, and any agents involved in the problem)?

```
controller: OS: Linux - 3.10.0-1160.41.1.el7.x86_64
agent: Linux RHEL 6.7
```

### Reproduction steps

- Store AWS credentials in jenkins (I tested using both username/password credentials and AWS credentials)
- Create a job to use these credentials:
```
withAWS(credentials: 'aws-s3-creds', region: 'us-east-1') {
s3Upload acl: 'Private',
bucket: 'some-bucket',
file: 'bm-test-file2'
}
```
- Configure jenkins to **NOT** run jobs as user `SYSTEM` - as recommended [by jenkins](https://www.jenkins.io/doc/book/security/build-authorization/)
- Ensure the user configured has permission to view the credentials

### Results

Expected result:

File uploaded to S3.
If the system is configured to run jobs as SYSTEM the jobs works as expected.
Even granting admin privileges to the user running the job is not sufficient. (And even it did that would defeat the purpose.)

Actual result:

Job fails:
```
java.lang.RuntimeException: Cannot find a Username with password credential with the ID aws-s3-creds
at de.taimos.pipeline.aws.WithAWSStep$Execution.withCredentials(WithAWSStep.java:372)
at de.taimos.pipeline.aws.WithAWSStep$Execution.start(WithAWSStep.java:301)
at org.jenkinsci.plugins.workflow.cps.DSL.invokeStep(DSL.java:319)
at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:193)
at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:122)
at jdk.internal.reflect.GeneratedMethodAccessor631.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1213)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1022)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:42)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:163)
at org.kohsuke.groovy.sandbox.GroovyInterceptor.onMethodCall(GroovyInterceptor.java:23)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:158)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:161)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:165)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:135)
at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:17)
at WorkflowScript.run(WorkflowScript:15)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.delegateAndExecute(ModelInterpreter.groovy:137)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.executeSingleStage(ModelInterpreter.groovy:666)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.catchRequiredContextForNode(ModelInterpreter.groovy:395)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.catchRequiredContextForNode(ModelInterpreter.groovy:393)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.executeSingleStage(ModelInterpreter.groovy:665)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:288)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.toolsBlock(ModelInterpreter.groovy:544)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.toolsBlock(ModelInterpreter.groovy:543)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:276)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(ModelInterpreter.groovy:443)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(ModelInterpreter.groovy:442)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:275)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withCredentialsBlock(ModelInterpreter.groovy:481)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withCredentialsBlock(ModelInterpreter.groovy:480)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:274)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.inDeclarativeAgent(ModelInterpreter.groovy:586)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.inDeclarativeAgent(ModelInterpreter.groovy:585)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:272)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.stageInput(ModelInterpreter.groovy:356)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.stageInput(ModelInterpreter.groovy:355)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:261)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.inWrappers(ModelInterpreter.groovy:618)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.inWrappers(ModelInterpreter.groovy:617)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:259)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(ModelInterpreter.groovy:443)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(ModelInterpreter.groovy:442)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(ModelInterpreter.groovy:254)
at ___cps.transform___(Native Method)
at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:86)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:113)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:83)
at jdk.internal.reflect.GeneratedMethodAccessor170.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.ClosureBlock.eval(ClosureBlock.java:46)
at com.cloudbees.groovy.cps.Next.step(Next.java:83)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:129)
at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:268)
at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:18)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:51)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:185)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:400)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$400(CpsThreadGroup.java:96)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:312)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:276)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:67)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:136)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
Finished: FAILURE
```