KerberosServiceAuthenticationProvider should convert GSSException

[BrunoEberhard]

In KerberosServiceAuthenticationProvider the method authenticate may throw GSSException. As GSSException is not a AuthenticationException this causes the ProviderManager to skip other AuthenticationProviders and lead to a 500 response in a web appliction.

GSSException is checked but not declared. See KerberosValidateAction run method. The acceptSecContext generates sometimes a GSSException.