[BUG] Cannot retrieve master key

**Describe the bug**
After creating the app for functions I can't get the master key, as an unexpected exception is raised.

***Exception or Stack Trace***
```
Exception in thread "main" java.lang.RuntimeException: com.fasterxml.jackson.core.JsonParseException: Unexpected character ('<' (code 60)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')
at [Source: (okhttp3.ResponseBody$BomAwareReader); line: 1, column: 2]
at rx.exceptions.Exceptions.propagate(Exceptions.java:57)
at rx.observables.BlockingObservable.blockForSingle(BlockingObservable.java:463)
at rx.observables.BlockingObservable.single(BlockingObservable.java:340)
at com.microsoft.azure.management.appservice.implementation.FunctionAppImpl.getMasterKey(FunctionAppImpl.java:227)
at it.unisa.fly.azure.Test.main(Test.java:55)
Caused by: com.fasterxml.jackson.core.JsonParseException: Unexpected character ('<' (code 60)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')
at [Source: (okhttp3.ResponseBody$BomAwareReader); line: 1, column: 2]
at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1804)
at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:663)
at com.fasterxml.jackson.core.base.ParserMinimalBase._reportUnexpectedChar(ParserMinimalBase.java:561)
at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._handleOddValue(ReaderBasedJsonParser.java:1892)
at com.fasterxml.jackson.core.json.ReaderBasedJsonParser.nextToken(ReaderBasedJsonParser.java:747)
at com.fasterxml.jackson.databind.ObjectReader._initForReading(ObjectReader.java:355)
at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:1596)
at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1203)
at com.microsoft.rest.serializer.JacksonConverterFactory$JacksonResponseBodyConverter.convert(JacksonConverterFactory.java:99)
at com.microsoft.rest.serializer.JacksonConverterFactory$JacksonResponseBodyConverter.convert(JacksonConverterFactory.java:88)
at retrofit2.ServiceMethod.toResponse(ServiceMethod.java:122)
at retrofit2.OkHttpCall.parseResponse(OkHttpCall.java:217)
at retrofit2.OkHttpCall.execute(OkHttpCall.java:180)
at retrofit2.adapter.rxjava.CallExecuteOnSubscribe.call(CallExecuteOnSubscribe.java:40)
at retrofit2.adapter.rxjava.CallExecuteOnSubscribe.call(CallExecuteOnSubscribe.java:24)
at retrofit2.adapter.rxjava.BodyOnSubscribe.call(BodyOnSubscribe.java:36)
at retrofit2.adapter.rxjava.BodyOnSubscribe.call(BodyOnSubscribe.java:28)
at rx.Observable.unsafeSubscribe(Observable.java:10327)
at rx.internal.operators.OnSubscribeMap.call(OnSubscribeMap.java:48)
at rx.internal.operators.OnSubscribeMap.call(OnSubscribeMap.java:33)
at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)
at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
at rx.Observable.subscribe(Observable.java:10423)
at rx.Observable.subscribe(Observable.java:10390)
at rx.observables.BlockingObservable.blockForSingle(BlockingObservable.java:443)
... 3 more
```

**To Reproduce**
Steps to reproduce the behavior:
Create an instance of the object azure than follow the code snippet

***Code Snippet***
```
ResourceGroup resourceGroup = azure.resourceGroups()
.define("rgthistest000")
.withRegion(Region.EUROPE_WEST)
.create();
System.out.println("Resource group created");
StorageAccount storageAccount = azure.storageAccounts()
.define("sathistest000")
.withRegion(Region.EUROPE_WEST)
.withExistingResourceGroup(resourceGroup)
.create();
System.out.println("Storage account created");
SkuDescription skuDescription = new SkuDescription()
.withName("Y1")
.withTier("Dynamic")
.withSize("Y1")
.withFamily("Y")
.withCapacity(0);
AppServicePlan appServicePlan = azure.appServices().appServicePlans()
.define("aspthistest000")
.withRegion(Region.EUROPE_WEST)
.withExistingResourceGroup(resourceGroup)
.withPricingTier(PricingTier.fromSkuDescription(skuDescription))
.withOperatingSystem(OperatingSystem.LINUX)
.withPerSiteScaling(false)
.create();
FunctionApp functionApp = azure.appServices().functionApps()
.define("thistest000")
.withExistingAppServicePlan(appServicePlan)
.withExistingResourceGroup(resourceGroup)
.withExistingStorageAccount(storageAccount)
.withAppSetting("FUNCTIONS_WORKER_RUNTIME", "python")
.withLocalGitSourceControl()
.create();
System.out.println("Function app created");

System.out.println(functionApp.getMasterKey()); //Exception is raised here
```

**Expected behavior**
I expected the master key to be returned

**Setup (please complete the following information):**
- OS: Linux
- IDE : Eclipse
- Version of the Library used
```

com.microsoft.azure
azure
1.21.0


commons-net
commons-net
3.3

Bắt đầu bằng cách tái hiện đoạn mã Java được cung cấp, tập trung vào FunctionApp.getMasterKey và mục nhập stack trace FunctionAppImpl.getMasterKey. Kiểm tra response trước khi Jackson phân tích nó, sau đó xác minh rằng lệnh gọi trả về khóa chính mong đợi thay vì response không phải JSON được báo cáo.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.