shill: portal: Recheck portal state

Introduce a retry interval for automatically retrying portal
checks.  Also provide a Manager API method for immediately
re-checking portal status.

BUG=chromium-os:27335
TEST=New unit tests, tested on real machine, including setting
PortaCheckInterval over DBus, and using Jason's addition to
test-flimflam for 'recheck-portal'.
Change-Id: Idc7def18c6f863859e94f4d4e9f266ab2670679c
Reviewed-on: https://gerrit.chromium.org/gerrit/17367
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_connection.h b/mock_connection.h
index 2d8af12..fdc1601 100644
--- a/mock_connection.h
+++ b/mock_connection.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -18,6 +18,7 @@
   virtual ~MockConnection();
 
   MOCK_METHOD1(UpdateFromIPConfig, void(const IPConfigRefPtr &config));
+  MOCK_CONST_METHOD0(is_default, bool());
   MOCK_METHOD1(SetIsDefault, void(bool is_default));
   MOCK_METHOD0(RequestRouting, void());
   MOCK_METHOD0(ReleaseRouting, void());