cellular: Add support for detecting connect/disconnect loop.

This is a workaround for the E362 modem and Verizon network.  When the
SIM runs out of credits, the modem may enter a connect/disconnect loop
with the Verizon network.  This CL detects this condition and prevents
the modem from indefinitely trying to auto-connect.

BUG=chrome-os-partner:18137
TEST=Unit tests, manually test code on a device that exhibits
connect/disconnect loop

Change-Id: I61ba52194f24fbe8199da7ed6f8cc746e36c5e9c
Reviewed-on: https://gerrit.chromium.org/gerrit/45162
Reviewed-by: Arman Uguray <armansito@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
Commit-Queue: Thieu Le <thieule@chromium.org>
diff --git a/mock_cellular.h b/mock_cellular.h
index 5e3eba5..9bb1d96 100644
--- a/mock_cellular.h
+++ b/mock_cellular.h
@@ -32,6 +32,7 @@
                ProxyFactory *proxy_factory);
   virtual ~MockCellular();
 
+  MOCK_METHOD1(Connect, void(Error *error));
   MOCK_METHOD1(Disconnect, void(Error *error));
   MOCK_METHOD3(OnDBusPropertiesChanged, void(
       const std::string &interface,