Make sure the accept mutex is released before calling child exit

hooks and cleanups.  Otherwise, modules can segfault in such code
and, with pthread mutexes, leave the server deadlocked.  Even if
the module doesn't segfault, if it performs extensive processing
it can temporarily prevent the server from accepting new
connections.

Reviewed by:	Jim, FirstBill


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@100018 13f79535-47bb-0310-9956-ffa450edef68