Add patch to avoid Flatpak test failures

Without this, we get test failures with this ostree if Avahi (or
dbus-daemon --system) is not available on the build/test system.

debian/changelog

@@ -6,6 +6,9 @@ ostree (2018.6-1) UNRELEASED; urgency=medium
     - d/libostree-1-1.symbols: Update
     - Build-depend on Avahi libraries
   * d/rules: Explicitly enable various desired libraries
+  * d/p/avahi-Fail-immediately-if-we-can-t-talk-to-D-Bus-or-Avahi.patch:
+    Add patch to avoid Flatpak test failures with this ostree if Avahi
+    (or dbus-daemon --system) is not available on the build/test system
 
  -- Simon McVittie <smcv@debian.org>  Fri, 08 Jun 2018 09:10:21 +0100