team: check return value of g_dbus_connection_call_sync()

The call can fail; in such case assume that an existing teamd died and
our instance will be able to continue.

https://bugzilla.redhat.com/show_bug.cgi?id=1347015

src/devices/team/nm-device-team.c

@@ -344,10 +344,18 @@ teamd_dbus_appeared (GDBusConnection *connection,
 		                                   2000,
 		                                   NULL,
 		                                   NULL);
-		g_variant_get (ret, "(u)", &pid);
 
-		if (pid != priv->teamd_pid)
+		if (ret) {
-			teamd_cleanup (device, FALSE);
+			g_variant_get (ret, "(u)", &pid);
+			if (pid != priv->teamd_pid)
+				teamd_cleanup (device, FALSE);
+		} else {
+			_LOGW (LOGD_TEAM, "failed to determine D-Bus name owner");
+			/* If we can't determine the bus name owner, don't kill our
+			 * teamd instance. Hopefully another existing teamd just died and
+			 * our instance will be able to grab the bus name.
+			 */
+		}
 	}
 
 	/* Grab a teamd control handle even if we aren't going to use it