CAS-1414: Expired TGT on ST generation does not invoke logout

In the event that TGT has expired (due to a very aggressive timeout), CAS currently does not initiate the logout protocol when a service requests comes in. This is because when the ST-grant logic is executed, the expired TGT is simply removed from the registry, rather than "destroyed" via the CAS API.
Merge branch 'master' into CAS-1414

Conflicts:
	cas-server-webapp-support/src/test/java/org/jasig/cas/web/flow/GenerateServiceTicketActionTests.java
CAS-1414: added missing final keywords
Merge pull request #417 from Unicon/CAS-1414

CAS-1414: Expired TGT on ST generation does not invoke logout