Warn instead of fail with wrong type_driver

Some of us are using custom type_drivers. Puppet code should allow
unexpected values for type_drivers.

Change-Id: I4a308ad379dee61260e3d27da2da00d7fce14e56
Signed-off-by: Arnaud Morin <arnaud.morin@corp.ovh.com>

manifests/plugins/ml2/type_driver.pp

@@ -130,6 +130,6 @@ define neutron::plugins::ml2::type_driver (
   }
   else {
     # detect an invalid type_drivers value
-    fail('type_driver unknown.')
+    warning('type_driver unknown.')
   }
 }

spec/classes/neutron_plugins_ml2_spec.rb

@@ -154,10 +154,9 @@ describe 'neutron::plugins::ml2' do
 
     context 'configure ml2 with bad driver value' do
       before :each do
+       scope.expects(:warning).with('type_driver unknown.')
        params.merge!(:type_drivers => ['foobar'])
       end
-
-      it_raises 'a Puppet::Error', /type_driver unknown./
     end
 
     context 'when using flat driver' do