Refs #5719 - wait for the cancel event being processed

For better feedback for the user that something happened.
Merge pull request #70 from iNecas/issue/6193

Fixes #6193 - make sure we increase the AR db pool soon enough
Merge pull request #69 from iNecas/issue/5719

Refs #5719 - wait for the cancel event being processed
Fixes #6193 - increase the db poll size only for executor