[client] KUDU-3472 Python client API to import JWT

This patch adds JWT to the Python client builder and to the
kudu.connect() methods.

Change-Id: Icaef1bd28efe9d47252bd211fb937f2e6e48cea9
Reviewed-on: http://gerrit.cloudera.org:8080/19862
Tested-by: Kudu Jenkins
Reviewed-by: Alexey Serbin <alexey@apache.org>
Reviewed-by: Zoltan Chovan <zchovan@cloudera.com>
5 files changed