[OVN] Delete NAT entry first on any FIP update
For now while updating FIP check if port or logical_ip
has changed and only then we deleted the NAT entry.
Unfortunately each time when FIP update occurs the
method _create_or_update_floatingip() is used. It first deletes
LSP pointed by FIP and adds it again along with new NAT entries.
Based on author comment this actions are required.
So if we don't update FIP with logical_ip or new port_id,
like update a description, the NAT entries gets duplicated.
Since all is wrapped withing a transaction and to not wait for
proper fix (this code need sa refactor based on commments with NAT
external_id column) I think thats safe just to delete the NAT entry
in such situation like described above.
(cherry picked from commit