RFR 8058849: test/sun/security/krb5/config/dns.sh needs to re-examined or replaced

[Weijun Wang]

Please review the fix at

    http://cr.openjdk.java.net/~weijun/8058849/webrev.00

The overridden NamingManager needs to return a Context object whose 
getAttributes() method returns hard coded data. Since Context includes a 
lot of interface methods, choosing a non-abstract child and only 
overriding its getAttributes() method will make the code much shorter. 
Before the fix, com.sun.jndi.dns.DnsContext is chosen but unfortunately 
it does not belong to java.naming module anymore. We now choose 
InitialDirContext instead.

Thanks
Max