Bug 30920: (QA follow-up) Use get_dirty_columns to avoid DB query

Bug 30920: (QA follow-up) Use get_dirty_columns to avoid DB query

We can rely on DBIC's get_dirty_columns to check if the descriptions
have changed, and set things for flushing without an extra DB query.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit a44f03c7156cce4ff1ae55da3772f98e7b5e89b6)
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>