Invalidate non-existing DBus proxy for power manager.

Upon observing an org.freedesktop.DBus.NameHasOwner signal, invalidate
the DBus proxy of the old power manager instance to avoid calling
UnregisterSuspendDelay on a non-existing instance.

BUG=chrome-os-partner:10380
TEST=Verify that wimax-manager does not call UnregisterSuspendDelay on
non-existing power manager instance.

Change-Id: I000c46f739e7ba174e95cc5d9b7b4d5e3704cfb6
Reviewed-on: https://gerrit.chromium.org/gerrit/25009
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
5 files changed