avahi: Fail immediately if we can't talk to D-Bus or Avahi

avahi: Fail immediately if we can't talk to D-Bus or Avahi

We special-case AVAHI_ERR_NO_DAEMON to not cause warnings, but if
we pass AVAHI_CLIENT_NO_FAIL to avahi_client_new, we never actually
see AVAHI_ERR_NO_DAEMON. Instead, we will get AVAHI_ERR_BAD_STATE
when we try to use the client.

Bug: https://github.com/ostreedev/ostree/issues/1618
Signed-off-by: Simon McVittie <smcv@debian.org>
Forwarded: https://github.com/ostreedev/ostree/pull/1639
Applied-upstream: 2018.7, commit:https://github.com/ostreedev/ostree/commit/e120a6b1198aaa785533c76316898f15a804dae1

Gbp-Pq: Name avahi-Fail-immediately-if-we-can-t-talk-to-D-Bus-or-Avahi.patch