NPE on ServletContainer when using Spring Boot with Jersey

* Framework version: 1.5
* Implementations: Spring Boot

## Scenario
Trying to run a Spring Boot with Jersey api

## Expected behavior
Returns successful response

## Actual behavior
Returns 502 Bad Gateway error

## Steps to reproduce
1. Deploy the lambda
1. Invoke the API

## Full log output
```
c.a.s.p.internal.LambdaContainerHandler : Error while handling request
java.lang.NullPointerException: null
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:365) ~[task/:na]
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:318) ~[task/:na]
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:205) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainManager$ServletExecutionFilter.doFilter(FilterChainManager.java:356) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:90) ~[task/:na]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:90) ~[task/:na]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:90) ~[task/:na]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[task/:na]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.FilterChainHolder.doFilter(FilterChainHolder.java:90) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.servlet.AwsLambdaServletContainerHandler.doFilter(AwsLambdaServletContainerHandler.java:156) ~[task/:na]
at com.amazonaws.serverless.proxy.spring.SpringBootLambdaContainerHandler.handleRequest(SpringBootLambdaContainerHandler.java:180) ~[task/:na]
at com.amazonaws.serverless.proxy.spring.SpringBootLambdaContainerHandler.handleRequest(SpringBootLambdaContainerHandler.java:53) ~[task/:na]
at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxy(LambdaContainerHandler.java:211) [task/:na]
at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxyStream(LambdaContainerHandler.java:254) [task/:na]
at com.capitalone.examples.aws.alb.lambda.StreamLambdaHandler.handleRequest(StreamLambdaHandler.java:30) [task/:na]
at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:909) [LambdaSandboxJava-1.0.jar:na]
at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:341) [LambdaSandboxJava-1.0.jar:na]
at lambdainternal.AWSLambda.(AWSLambda.java:63) [LambdaSandboxJava-1.0.jar:na]
at java.lang.Class.forName0(Native Method) [na:1.8.0_201]
at java.lang.Class.forName(Class.java:348) [na:1.8.0_201]
at lambdainternal.LambdaRTEntry.main(LambdaRTEntry.java:119) [LambdaJavaRTEntry-1.0.jar:na]
```