shill: teach dbus_adaptor (and appropriate subclasses) how
to clear properties

BUG=chromium-os:24814
TEST=new unit tests

Change-Id: Ifad5ad0ad6c00d906bade7e1293540a58ac15625
Reviewed-on: https://gerrit.chromium.org/gerrit/15291
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: mukesh agrawal <quiche@chromium.org>
diff --git a/service_dbus_adaptor.cc b/service_dbus_adaptor.cc
index fe11dd5..6a54471 100644
--- a/service_dbus_adaptor.cc
+++ b/service_dbus_adaptor.cc
@@ -72,10 +72,8 @@
 }
 
 void ServiceDBusAdaptor::ClearProperty(const string &name,
-                                       ::DBus::Error &/*error*/) {
-  NOTIMPLEMENTED() << " Ignorning request to clear " << name
-                   << " property of Service " << service_->UniqueName()
-                   << " (aka " << service_->friendly_name() << ")";
+                                       ::DBus::Error &error) {
+  DBusAdaptor::ClearProperty(service_->mutable_store(), name, &error);
 }
 
 void ServiceDBusAdaptor::Connect(::DBus::Error &error) {