Feat!: Update JJB version to 6x

Feat!: Update JJB version to 6x

Jenkins Job Builder 6.0.0 is released and breaks backward
compatibility with 5.1.0.

The breaking changes with previous 5.1.0 release:

- Jobs are now expanded the same way as job templates.
- Macros without parameters are now expanded the same way as macros
  with parameters.
- Tags !include-raw: and !include-raw-escape: should now be used the
  same way in jobs and macros without parameters as they are used in
  job templates and macros with parameters.
- Fix shellcheck warnings
Ref:
https://storyboard.openstack.org/#!/story/2010963
https://storyboard.openstack.org/#!/story/2010588

Issue: LF-JIRA RELENG-5119
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>
Change-Id: I9c16d62bf40c1396a630b479dca12a62a6e48c56
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>