Improving handling of rename operation by user tracker, together with
fixes for user tests, that failed as consequence.
Failures were caused by RFE Kerberos principal alias.
Some tests were rewritten, since they used "--setattr" option instead of
"--rename", and hence didn't reflect proper behaviour of the principal
aliases feature.
https://fedorahosted.org/freeipa/ticket/6024
Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>