mpm_event: follow up to r1538490, r1545736, r1604350, r1639614 and r1642868.

Clear and restore sbh in notify_suspend() and notify_resume() respectively.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1663017 13f79535-47bb-0310-9956-ffa450edef68