This commit create dedicated Jenkins jobs for 6.x for master branch and
PRs. This is required to allow having different test suites for 7.x and
6.x in a following PR.
Add JJBB job definitions to the repo so they can be managed here.
Modified jobs so they will auto-generate the `inject-passwords` section
containing `VAULT_ROLE_ID`, `VAULT_SECRET_ID` and `VAULT_ADDR`.
