Make sure that workflow publish always publishes the 'master' document branch

When the current preview is for a branch (say Christmas), publication is disabled. However, there might already be a request for publication on the master (core) version.

When this request is triggered/fires, it should not just publish the 'unpublished' variant since that might be a branch version. Instead, it should publish the right master-preview version. The publish in case the unpublished is for a branch really is similar to 'reintegrate'