memcached: add support for group deletion

Change-Id: Iff0e41180a212b56040f1142c499266a1c522f3d
tests: minor code simplification

Change-Id: I976bbe79327de233edb1b4c448572d23a1e743ac
redis: add support for group deletion

Change-Id: Ia86213d15f58f2842106ce4571d3f654adb519e9
zookeeper: add support for delete group

Change-Id: I21dd62c93dd3d3394c549245b1d8d2633979927d