Kerberos ticket renewal fix in JDBC Interpreter

It is observed in the JDBC Interpreter that Kerberos ticket renewal thread and interpret() function vies for Kerberos ticket during Interpreter initialization and later on, during the ticket renewal. The following observations were noticed:

1. Invalid Kerberos ticket with Interpreter; queries will start to fail after few days
2. Uninitialized UGI being used in the beginning; first login always happens to be with auth:UNIX which is wrong
3. Ticket renewal thread (runKerberosLogin() function) exhausts the max attempts without giving a chance to acquire a ticket