hibernate idle xmem processes

Change-Id: I07e4dbbc40cb38e3068566a13c470995d0798d15
Reviewed-on: http://review.couchbase.org/30359
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Junyi Xie <junyi.couchbase@gmail.com>