CBQE-928: reset clien in case MemcachedError for getMeta

Change-Id: I6d3595e0b83753207be06a2fdf5064233f699d9d
Reviewed-on: http://review.couchbase.org/24198
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>