s3:client: avoid using cli->{use_kerberos,...} for cli_session_creds_init() in smbspool.c

s3:client: avoid using cli->{use_kerberos,...} for cli_session_creds_init() in smbspool.c

CLI_FULL_CONNECTION_USE_KERBEROS is the only possible flag the
caller of smb_complete_connection() will pass, so we can avoid
use it directly instead of going via cli_start_connection()
to use cli->use_kerberos.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>