Merge r1200977 from trunk:

don't let thread-scope be selected in a server w/o threads


Submitted by: covener
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1200983 13f79535-47bb-0310-9956-ffa450edef68