When managing AD objects the SID of the objects are stored in FreeIPA
database, but a user would still use the human readable values, like
"AD\\user" or "user@ad.domain". This can cause idempotence issues in
many cases, and prevent some actions to be performed, like ensure
absence of the object.

The methods added allow the conversion of one or multiple objects, and
will be used by any module that manages AD objects.

Signed-off-by: Rafael Guterres Jeffman <rjeffman@redhat.com>