ABFS: Fix idempotency test failures when SharedKey is set as AuthType

Idempotency related tests added as part of 

https://issues.apache.org/jira/browse/HADOOP-17015

create a test AbfsClient instance. This mock instance wrongly accepts valid sharedKey and oauth token provider instance. This leads to test failures with exceptions:
[ERROR] testRenameRetryFailureAsHTTP404(org.apache.hadoop.fs.azurebfs.ITestAzureBlobFileSystemRename)  Time elapsed: 9.133 s  <<< ERROR!
Invalid auth type: SharedKey is being used, expecting OAuth
        at org.apache.hadoop.fs.azurebfs.AbfsConfiguration.getTokenProvider(AbfsConfiguration.java:643)
This Jira is to fix these tests.