Fix wrong response from new-topic using redis

The MemcachedBagOStuff and RedisBagOStuff interfaces do
not match, specifically the getMulti method of memcached
does not return unfound keys, where the redis one returns
the key set to false.

Change-Id: I6d81d4a1bc6745e9894ba525de258a970f3d8d94
Merge "Fix wrong response from new-topic using redis"