fix the getKrb5Vars() method to use the renamed variables
Since pipeline-as-a-service!13 the KRB5_KDC_HOST, KRB5_ADMIN_HOST, and
KRB5_KPASSWD_HOST variables have been removed, and replaced with a single
KRB5_HOST variable. References to the different services are constructed by
appending the service-specific _PORT variable to the KRB5_HOST variable,
separated by a colon.