Remove requirement to specify TenantGuid for MSI Token Provider

The MSI identity extension on Azure VMs has removed the need to specify the tenant guid as part of the request to retrieve token from MSI service on the local VM. This means the tenant guid configuration parameter is not needed anymore. This change removes the redundant configuration parameter.

It also makes the port number optional - if not specified, then the default port is used by the ADLS SDK (happens to be 50342, but that is transparent to Hadoop code).