sysdb: Search also aliases in sysdb_search_object_by_name
sysdb_search_object_by_name did not work well case insensitive domain.
Resolves:
https://fedorahosted.org/sssd/ticket/3284
Reviewed-by: Pavel Březina <pbrezina@redhat.com>
(cherry picked from commit 8a4a2b87f51462ac22bf6db93927484841f098c6)