flimflam-test: Fix syntax error in mm-disconnect

This triggers pylint warnings and even a cursory glance reveals that
this would trigger an exception at runtime.  This was apparently broken
in b9582b442509904e4b18ba6f40fc4e47f6b858db when the line defining
manager was removed in a refactoring.

TEST=Pylint no longer complains
BUG=None

Change-Id: Ieb055f7fb5a379b107f98c83b6b3b3191ae59a04
Reviewed-on: https://gerrit.chromium.org/gerrit/42155
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Thieu Le <thieule@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
diff --git a/test/mm-disconnect b/test/mm-disconnect
index e4e3fe9..d13dcaf 100755
--- a/test/mm-disconnect
+++ b/test/mm-disconnect
@@ -31,7 +31,7 @@
 if waitflag:
     bus = dbus.SystemBus()
     bus.add_signal_receiver(state_changed,
-                            bus_name=manager.provider,
+                            bus_name=mm.ModemManager.INTERFACE,
                             signal_name="StateChanged",
                             path_keyword="path")