When deciding on the default address family for listening sockets,

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