CBQE-2096 fix broken in add, rm and failover
node if there is not key 'group' in 'cluster'

Change-Id: I37a2a37e5cfc82da38c2f5379d9531381a07c9d2
Reviewed-on: http://review.couchbase.org/34195
Tested-by: Thuan Nguyen <soccon@gmail.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>