While running tests, the D-Bus library was set to call _exit() when the
client leaves the bus. This caused the second test to be interrupted
without providing a PASS/FAIL result. This was confirmed by running
test-sdp with DBUS_VERBOSE=1.
This commit disables this behavior, which does not exist on BlueZ
because g_dbus_set_disconnect_function() implicitly does this.
If g_dbus_setup_private() fails (e.g. a session bus is not available,
and there is no X11 for dbus-launch to work), the tests are silently
skipped.
With this commit, the D-Bus error message is also printed if verbose
mode is enabled. The test is still skipped as before.
