ABFS: eTag Check to mitigate Rename Failures

RenameFilePath on its first try receives a Request timed out error with code 500. On retrying the same operation, a Source file not found (404) error is received. 

Possible temporary mitigation: Check whether etags remain the same before and after the retry and accordingly send an Operation Successful result, instead of source file not found. For this, adding a check and an additional call to get the source eTag, in case it is not present already, to check after a rename retry whether the source and destination eTags match.