Some changes require updating the existing entities in a
clear and transparent way for the user.
This patch adds a mechanism to create separate tasks that
can run periodically or just once in order to update or
modify existing entities that require changes after a new
patch or RFE.
As an example, a first task has been included for updating
existing OVN LB HM ports, changing their device_owner, and
adding their device_id.
Closes-Bug: 2038091
Change-Id: I0d4feb1e5c128d5a768d1b87deb2dcb3ab6d1ea1
1661f3815c