ipatests: legacy_clients: Test legacy clients with non-posix trust
    
    Adds test cases for legacy client support with IPA that has estabilish
    trust with AD that does not leverage POSIX attributes defined on AD.
    
    https://fedorahosted.org/freeipa/ticket/4134
    
    Reviewed-By: Nathaniel McCallum <npmccallum@redhat.com>