shill: Enable and disable reverse-path filtering

When an http proxy request is active (as well as portal check, when
that gets written), we need to initiate connections over a non-default
network interface.  For this we temporarily disable reverse-path
filtering on the interface during the duration of the request.

BUG=chromium-os:24141
TEST=New unit tests for HTTPProxy and Connection

Change-Id: Ife2ad775fd8a3d2fb48f860e804eeb442dc5c58a
Reviewed-on: https://gerrit.chromium.org/gerrit/12889
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
diff --git a/mock_routing_table.h b/mock_routing_table.h
index 1afd37e..9eaa870 100644
--- a/mock_routing_table.h
+++ b/mock_routing_table.h
@@ -28,6 +28,7 @@
                                      const IPConfigRefPtr &ipconfig,
                                      uint32 metric));
   MOCK_METHOD1(FlushRoutes, void(int interface_index));
+  MOCK_METHOD0(FlushCache, bool());
   MOCK_METHOD1(ResetTable, void(int interface_index));
   MOCK_METHOD2(SetDefaultMetric, void(int interface_index, uint32 metric));