Merge r1629916 from trunk:

core: follow up to r1629909: ap_daemons_to_start can't be lower than 1 (not 0) for prefork either.
Submitted by: ylavic
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1707035 13f79535-47bb-0310-9956-ffa450edef68