make sure we can actually bind to an AF_INET6 socket before
deciding that we should default to AF_INET6. This fixes a startup
problem on certain levels of OpenUNIX.
PR: 10235
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96237 13f79535-47bb-0310-9956-ffa450edef68