Fix a segfault when a numeric host (e.g., "Host: 123") was specified.

apr_parse_addr_port() assumes that if there is just a number it must
be a port, but here we need to assume that it is a host.

todo: pass a flag into apr_parse_addr_port()?  unclear whether or
      not that is cleaner overall


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@90734 13f79535-47bb-0310-9956-ffa450edef68