Need to check if the userdir is absolute before it gets split apart by ap_getword()

Also fixed up the !HAVE_DRIVE_LETTERS case (such as NetWare) where
the volume delimiter ( colon ) is not in an absolute position.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93780 13f79535-47bb-0310-9956-ffa450edef68