Merge r1663017 from trunk:

mpm_event: follow up to r1538490, r1545736, r1604350, r1639614 and r1642868.
Clear and restore sbh in notify_suspend() and notify_resume() respectively.

Submitted by: ylavic
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1664365 13f79535-47bb-0310-9956-ffa450edef68