Changeset 822e9bd for commands.c

Fix SASL digest-uri to be acceptable to ejabberd.

This is, approximately, 68ad6bc and 8fe68e0 from the XML-Stream
repo.  The problem is that, if example.com pointed SRV records at
foo.example.com, we'd send "xmpp/foo.example.com" (which is, arguably,
what RFC 2831 calls for, but community consensus seems to disagree)
rather than "xmpp/example.com".

ejabberd would also accept "xmpp/foo.example.com/example.com", and
that would follow RFC 2831 more closely, but I don't want to introduce
divergence from the upstream unless there's an observed interoperability
problem that would be fixed by it.