KUDU-3496 support spnego dedicated keytab

Add a --spnego_keytab_file flag for seperation of service keytab file
and spnego keytab file. If --webserver_require_spnego flag is true and
--spnego_keytab_file is not empty but specifies a keytab location, web
console gss acceptor registers specified keytab location so that web
server is able to find spnego principal from spnego_keytab_file. if
--spnego_keytab_file is empty even --webserver_require_spnego=true, web
server will use --keytab_file flag as it is.

Change-Id: I01646207954854d67308f99e6b71ba32c019ed6a
Reviewed-on: http://gerrit.cloudera.org:8080/20278
Tested-by: Kudu Jenkins
Reviewed-by: Attila Bukor <abukor@apache.org>
5 files changed