merge from trunk:

  worker and event MPMs: fix excessive forking if fork() or child_init
  take a long time.

PR: 39275
Reviewed by: trawick, gregames, pquerna


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@424874 13f79535-47bb-0310-9956-ffa450edef68