MB-32106: Allow for statistics-related mctimings
MB-32106: Allow for statistics-related mctimings

to_opcode throws an exception if the string can't be mapped
to a string and not the invalid opcode. Catch the exception
and try the stats-related one instead.

Change-Id: I42c62c6c74a1bbf805a9743601b3d4141ea52077
Reviewed-on: http://review.couchbase.org/102024
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine