Previously one could not speculatively add a project to a dependent
pipeline if the desired queue did not exist. This change handles this
special case by creating a dynamic queue for the use of the speculative
change. If the change merges, then the queue will exist for any future
change.
Introduces a new ChangeQueue attribute, 'dynamic', to help
DependentPipelineManager objects determine whether a ChangeQueue was
created dynamically or not, during a clean up phase. Only used in
DependentPipelineManager pipelines.
Note that this doesn't necessarily support a newly added named queue, or
adding a project to an existing named queue. That will be follow up
work.
Change-Id: I51ab7fb113f1bcbcef5f4f6c96ca046d0c76fdd9
Story: 2000898
Task: 3528
78f544a813