Support Specifying Domain Name for Kerberos Authentication.

[bhunut-adobe]

Summary

By default the ldap3 library attempts to bind against the service principal for the domain you attempted to connect to. If your target LDAP service uses a round-robin DNS, it’s likely that the hostname you connect to won’t match. This cause it to throw the following error:
LDAP connection failure: SSPI: InitializeSecurityContext: The specified target is unknown or unreachable

In this case, you can either specify Domain Controller hostname or force the library to do a reverse DNS lookup.

This PR includes the fix to do a reverse DNS lookup automatically when using Kerberos Authentication Method by simply pass True as the first element in sasl_credentials to do a reverse DNS lookup.

There is no additional configuration end-user have to do. This solution supported Domain Controller FQDN and Domain Name

Testing Steps

• Set Authentication Method in Connector-LDAP.yml to Kerberos
• Change Host Value in Connector-LDAP.yml to Domain Name (ldaps://example.com)
• Run UST
• It should authenticate to AD and Pull Users and Groups

• Set Authentication Method in Connector-LDAP.yml to Kerberos
• Change Host Value in Connector-LDAP.yml to Domain Controller FQDN (ldaps://dc001.example.com)
• Run UST
• It should authenticate to AD and Pull Users and Groups

Fixes #654