MB-21475: Account for memory alloc/dealloc in stopTaskGroup
MB-21475: Account for memory alloc/dealloc in stopTaskGroup

While stopping a task group, any memory allocations/deallocations made
should be accounted to the bucket in question.  Hence no
`onSwitchThread(NULL)` call.

(Note: This is very similar to MB-20054).

Change-Id: Ib5f88fe8e4061ac827a28e267717df32131aba23
Reviewed-on: http://review.couchbase.org/69184
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Daniel Owen <b3fc0e1a51f252986e60be7da121b74d3ac6845f@couchbase.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

daverigby/kv_engine,daverigby/ep-engine,daverigby/kv_engine,daverigby/kv_engine,couchbase/ep-engine,daverigby/kv_engine,membase/ep-engine,daverigby/ep-engine,membase/ep-engine,daverigby/ep-engine,couchbase/ep-engine,membase/ep-engine,membase/ep-engine,daverigby/ep-engine,couchbase/ep-engine,couchbase/ep-engine