Remove redundant tests from com/sun/security/sasl/gsskerb

The following manual tests seem redundant:
com/sun/security/sasl/gsskerb/AuthOnly.java
com/sun/security/sasl/gsskerb/ConfSecurityLayer.java
com/sun/security/sasl/gsskerb/NoSecurityLayer.java

These scenarios are in the problem list, but also are already covered by the automated test in test/jdk/sun/security/krb5/auto/SaslBasic.java. Therefore, the previously mentioned manual tests, which require a manual KDC setup and offer no additional value, can be removed.