CBQE-1220 fix the bug for retry for cbstats

Change-Id: Ifb030bce66ef26e85069088228465f9231e27561
Reviewed-on: http://review.couchbase.org/26810
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>
Tested-by: Chisheng Hong <chisheng@couchbase.com>