If we're given a wildcard address, we can't announce it like that: we need
to try to turn it into a real address (using guess_address). Then we
use that address. As a side-effect of this cleanup, we only announce
*any* '--addr' if it's routable.
This fix means that our tests have to force '--announce-addr' because
otherwise localhost isn't routable.
This means that gossipd really controls the addresses now, and breaks
them into two arrays: what we bind to, and what we announce. That is
now what we return to the master for json_getinfo(), which prints them
as 'bindings' and 'addresses' respectively.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>