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/ipconfig_dbus_adaptor.cc b/ipconfig_dbus_adaptor.cc
index 912c42d..7a8b60f 100644
--- a/ipconfig_dbus_adaptor.cc
+++ b/ipconfig_dbus_adaptor.cc
@@ -78,11 +78,8 @@
 }
 
 void IPConfigDBusAdaptor::ClearProperty(const std::string &name,
-                                        ::DBus::Error &/*error*/) {
-  NOTIMPLEMENTED() << " Ignoring request to clear " << name
-                   << " property of IPConfig " << ipconfig_->serial()
-                   << " (associated with Device " << ipconfig_->device_name()
-                   << ")";
+                                        ::DBus::Error &error) {
+  DBusAdaptor::ClearProperty(ipconfig_->mutable_store(), name, &error);
 }
 
 void IPConfigDBusAdaptor::Remove(::DBus::Error &/*error*/) {