* modules/core/mod_watchdog.c: Switch to simpler logic to avoid the

* modules/core/mod_watchdog.c: Switch to simpler logic to avoid the
  thread cleanup running before the thread has started, avoiding
  mutex operations which both have undefined behaviour:

  a) double-locking an UNNESTED (non-recursive) mutex twice in the parent
  b) unlocking a mutex in the spawned thread which was locked by the parent

  (wd_startup, wd_worker_cleanup, wd_worker): Use a boolean to ensure
  the cleanup does nothing if the thread wasn't started, drop the mutex.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1876511 13f79535-47bb-0310-9956-ffa450edef68