mod_isapi: GetServerVariable returned improperly terminated header

fields given "ALL_HTTP" or "ALL_RAW".

PR:		20656
Submitted by:	Jesse Pelton <jsp pkc.com>
Reviewed by:	Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@102643 13f79535-47bb-0310-9956-ffa450edef68