shill: enable (don't disable) -Wunused

having fixed an unused parameter in the dbus-c++ headers, those
headers no longer have unused parameters. so, if we fix up unused
parameters in shill code, we can compile with -Wunused. (this is
implied by -Wall, as long as we don't override with -Wno-unused.)

BUG=chromium-os:20779
TEST=unittests

- comment out unused parameters in function definitions
- remove some unused local variables
- also: fix an old-style cast

Change-Id: Ie654a7b34d622cecb0f26bd47c17813fe8423001
Reviewed-on: http://gerrit.chromium.org/gerrit/8365
Tested-by: mukesh agrawal <quiche@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
diff --git a/dbus_adaptor.cc b/dbus_adaptor.cc
index 808b325..d1c082d 100644
--- a/dbus_adaptor.cc
+++ b/dbus_adaptor.cc
@@ -84,7 +84,7 @@
 // static
 bool DBusAdaptor::GetProperties(const PropertyStore &store,
                                 map<string, ::DBus::Variant> *out,
-                                ::DBus::Error *error) {
+                                ::DBus::Error */*error*/) {
   {
     PropertyConstIterator<bool> it = store.GetBoolPropertiesIter();
     for ( ; !it.AtEnd(); it.Advance())