Ticket 47421 - memory leaks in set_krb5_creds
Bug Description: Valgrind shows memory leaks in set_krb5_creds()
Fix description: krb5_unparse_name() allocates/returns the principle name.
But we can call this function twice without freeing the first
returned value.
https://fedorahosted.org/389/ticket/47421
Reviewed by: richm(Thanks!)