Release the memory allocated for command entries

Change-Id: I334df841ddddbbee5c3311d5fc51650e3293b4b3
Reviewed-on: http://review.couchbase.org/27342
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>