Changed signature of request validator validateScope() method

The previous method signature of validateScope() took in the full parameter map from the request, and re-parsed the scope out of that. However, in both places this method is called, the resolved Set<String> of scopes is available off of a request object (TokenRequest or AuthorizationRequest). That scope set is more accurate than the set visible in the request.getParameters() map. This patch alters the method signature to take in the request scope Set directly instead of re-parsing it. 

JIRA issue: https://jira.springsource.org/browse/SECOAUTH-421