tests: use dbus-run-session instead of dbus-launch to run tests
tests: use dbus-run-session instead of dbus-launch to run tests

The use of dbus-launch is deprecated by dbus upstream.
See https://lists.debian.org/debian-devel/2016/08/msg00554.html for more
details.

So use dbus-run-session instead, which was specifically designed to be
used for such cases, like running test-suites.

See also https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=836049.

https://bugzilla.gnome.org/show_bug.cgi?id=770798

pexip/pygobject,GNOME/pygobject,pexip/pygobject,GNOME/pygobject,GNOME/pygobject,pexip/pygobject