container: Make missing dbus module non-fatal

This is required to properly support Waydroid tool versions <=1.3.4
(which NixOS for example still has), or 1.4.0+ configured with
USE_DBUS_ACTIVATION=0 (basically non-systemd distributions which can't
supervise the container properly when it's launched via D-Bus)

tools/container.py

@@ -1,7 +1,10 @@
-import dbus
+try:
+    import dbus
+except ModuleNotFoundError:
+    pass
 
 def DBusContainerService(object_path="/ContainerManager", intf="id.waydro.ContainerManager"):
     return dbus.Interface(dbus.SystemBus().get_object("id.waydro.Container", object_path), intf)
 
 def DBusSessionService(object_path="/SessionManager", intf="id.waydro.SessionManager"):
-    return dbus.Interface(dbus.SessionBus().get_object("id.waydro.Session", object_path), intf)
+    return dbus.Interface(dbus.SessionBus().get_object("id.waydro.Session", object_path), intf)