util: pull jwt code from Impala

Change-Id: Ib546762aa7ff53009f32688c30c5642ee4df494b
Reviewed-on: http://gerrit.cloudera.org:8080/18467
Reviewed-by: Alexey Serbin <alexey@apache.org>
Reviewed-by: Wenzhe Zhou <wzhou@cloudera.com>
Tested-by: Kudu Jenkins
6 files changed