Pipeline jobs in in Jenkins 2.x appear as placeholder tasks for their
entire lifetime when queried via the API. The fix for #1659787
introduced completly ignoring placeholder tasks. Thus pipeline jobs are
never included in the list returned by get_running_builds.
This commit will change the behaviour of get_running_builds as follows:
- Placeholder tasks will be included: So running pipeline jobs
will be included.
- Builds which do not have a build number yet will be ignored:
This prevents the exception described in #1659787.
Change-Id: I30351ec78d6186b0674e3c08be00076b0ce2333e
Closes-Bug: #1750372
Related-Bug: #1659787