shill: wimax: Monitor for WiMaxManager's presence on DBus.

Reset WiMaxProvider's state by destroying all WiMax devices when WiMaxManager
disappears. Connect to WiMaxManager only if its present. This makes shill more
resilient against wimax_manager crashes.

BUG=chrome-os-partner:10948
TEST=unit tests

Change-Id: I0a79d44fd19d6decc0b3964a144e6358711cd8b6
Reviewed-on: https://gerrit.chromium.org/gerrit/26665
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
diff --git a/manager.h b/manager.h
index 4e275d6..b3f45e3 100644
--- a/manager.h
+++ b/manager.h
@@ -233,6 +233,7 @@
   friend class ManagerAdaptorInterface;
   friend class ManagerTest;
   friend class WiFiObjectTest;
+  friend class WiMaxProviderTest;
   FRIEND_TEST(ManagerTest, AvailableTechnologies);
   FRIEND_TEST(ManagerTest, CalculateStateOffline);
   FRIEND_TEST(ManagerTest, CalculateStateOnline);