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/cellular_service.cc b/cellular_service.cc
index 26556d3..f2c2b10 100644
--- a/cellular_service.cc
+++ b/cellular_service.cc
@@ -23,10 +23,9 @@
                                  EventDispatcher *dispatcher,
                                  Manager *manager,
                                  const CellularRefPtr &device)
-    : Service(control_interface, dispatcher, manager),
+    : Service(control_interface, dispatcher, manager, flimflam::kTypeCellular),
       strength_(0),
-      cellular_(device),
-      type_(flimflam::kTypeCellular) {
+      cellular_(device) {
   PropertyStore *store = this->mutable_store();
   store->RegisterConstString(flimflam::kActivationStateProperty,
                              &activation_state_);
@@ -40,7 +39,6 @@
   store->RegisterConstStringmap(flimflam::kServingOperatorProperty,
                                 &serving_operator_.ToDict());
   store->RegisterConstUint8(flimflam::kSignalStrengthProperty, &strength_);
-  store->RegisterConstString(flimflam::kTypeProperty, &type_);
   store->RegisterConstString(flimflam::kUsageURLProperty, &usage_url_);
 }