[Feature] Support job dismiss operation

[fmigneault]

Cancel the execution of an accepted or running job.

• Make sure of handling of the resulting status works as intended ([BUG] Job status inconsistencies #145).
• Must also add the corresponding conformance item when implemented (Conformance route #53).
• Processes should advertise that this is possible with dismiss in jobControlOptions of their description response.
• See celery task revoke: https://stackoverflow.com/a/8924116/5936364