worker MPM: Don't forcibly kill worker threads if the child process is
exiting gracefully.

Submitted by: Oracle, via trawick

This modification was made some years ago for Oracle HTTP Server
by an Oracle employee.

Proposed by: trawick
Reviewed by: jim, rjung

Backport of r1526220 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1528962 13f79535-47bb-0310-9956-ffa450edef68