mpm_event: remove atomics for timeout_queue's total counter.

It's always updated under the timeout_mutex lock, or read for logging and
scoreboard updates (not critical).

For the read cases a volatile access is enough, while removing the atomic ops
for the already protected write cases saves cycles and context switches.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1819853 13f79535-47bb-0310-9956-ffa450edef68