Applied backport.

Close PR 50861 where enabling and disabling of buffered
logs can cause a segfault.
Patch by: Torsten Förtsch <torsten.foertsch@gmx.net>
Reviewed by: sf, trawick, rjung


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1195004 13f79535-47bb-0310-9956-ffa450edef68