qpid-route uses machine hostname if host not given

When a broker address is not supplied to qpid-route, it attempts to use the machines hostname as the broker address. This works well when the hostname is translatable to an ip address. However, when the hostname has been set to a non-translatable string, qpid-route fails.

For backwards compatability, qpid-route should continue to use hostname when the broker address is not supplied, but if hostname is not a valid address, qpid-route should default to "localhost".