[9] RFR: 8048138: Tests for JAAS callbacks

[Artem Smotrakov]

Hello,

Please review a couple of new tests for JAAS:
- StandardCallbacks.java is for standard JAAS callbacks (except 
RealmCallback and RealmChoiceCallback since the test is not about Sasl, 
and actually those two callback extends ChoiceCallback which is used in 
the test)
- SharedState.java checks if a shared state is passed to login modules

Bug: https://bugs.openjdk.java.net/browse/JDK-8048138
Webrev: http://cr.openjdk.java.net/~asmotrak/8048138/webrev.00/

Artem