Add basic set of clustered LDAP tests

This is an initial set of tests to cover very basic AD funcitonality
in a clustered enviornment.

The tests join AD, verify that AD users/groups are visible on
all cluster nodes, verify that kerberos settings are configured
correctly on all cluster nodes, then leaves the activedirectory
domain and verifies that the cluster no longer reports as being
joined to activedirectory.