Add enablement flags to classes managing Nova DB records purging and
archieving. With that change, cron jobs can be removed, if no longer
needed. For example, when the cron jobs were originally enabled but
later will be disabled so that users can always restore any deleted
instances.
Co-authored-by: Takashi Kajinami <tkajinam@redhat.com>
Signed-off-by: Bogdan Dobrelya <bdobreli@redhat.com>
Change-Id: I4b2c65b91b83c7ac64f909359585aa76c19d4705