MB-31513 Implement Hashtable::visit() using ::pauseResumeVisit()
MB-31513 Implement Hashtable::visit() using ::pauseResumeVisit()

Reimplement Hashtable::visit() to use Hashtable::pauseResumeVisit()
for easier maintenance of Hashtable::visit().

Change-Id: I1b843e1256ad0a09324938150fcc6a1fdebc75be
Reviewed-on: http://review.couchbase.org/100315
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