shill: implement Manager.GetService (error-case only)

BUG=chromium-os:20254
TEST=unittests, WiFiManager/000_SSID_Length_Limit

this gives us enough to pass the autotest for
network_WiFiManager/000_SSID_Length_Limit.

Change-Id: Ib0305e707d2203327d846be3e0b206033d6a884a
Reviewed-on: http://gerrit.chromium.org/gerrit/7567
Commit-Ready: mukesh agrawal <quiche@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
diff --git a/service_unittest.cc b/service_unittest.cc
index 35063f0..efbd149 100644
--- a/service_unittest.cc
+++ b/service_unittest.cc
@@ -45,7 +45,7 @@
   ServiceUnderTest(ControlInterface *control_interface,
                    EventDispatcher *dispatcher,
                    Manager *manager)
-      : Service(control_interface, dispatcher, manager) {}
+      : Service(control_interface, dispatcher, manager, "stub") {}
   virtual ~ServiceUnderTest() {}
 
   virtual void Connect(Error *error) {}