Instead of parametrising an instance of org.apache.cxf.policy.PolicyInterceptorProviderImpl
we use this class to reduce the impact of changes to the addressing metadata namespace
(only need to update Metadataconstants, otherwise cfg file fragement also).
Helper method to determine if an MAPs Action is empty (a null action
is considered empty, whereas a zero length action suppresses
the propagation of the Action property).