Reduce default timeout to 300 seconds all around. Not reduced further

because there are still likely some odd snippets of code that don't
properly reset the timer.

Reviewed by: Dean Gaudet, Jim Jagielski, Randy Terbush


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@77615 13f79535-47bb-0310-9956-ffa450edef68