do not import memcache on client
Fixes regression caused by cd3ca94ff2ef738cb3a9eae502193413058f976d.
Which caused:
* client installation failure (missing memcache)
* invalid warning in CLI on server
https://fedorahosted.org/freeipa/ticket/5133
Reviewed-By: Tomas Babej <tbabej@redhat.com>