Merge r484978,r484787,r484792 from trunk:

* Isolate the unlock return vals

* Log when the lock fails.

* Failure to unlock is very nasty, so log it to help with troubleshooting.

Submitted by: jim
Reviewed by: jim, rpluem, wrowe


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@488822 13f79535-47bb-0310-9956-ffa450edef68