example/mcc: use lcb_run_loop/lcb_stop_loop()

While these functions are declared 'LCB_INTERNAL_API' they are less
wrong than accessing the IOPS itself

Change-Id: I1ab89e90dbcad9fbeecd300c8124ad58c9326699
Reviewed-on: http://review.couchbase.org/36280
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>