Fix DVR interface delete by port when gateway is set
When removing a DVR interface by port, the subnet_id
passed to delete_csnat_router_interface_ports is None,
and so it deletes all the DVR SNAT ports for the
router.
This patch fixes this issue by passing in the right
subnet_id to the delete_csnat_router_interface_ports.
Change-Id: I16735195c6575454876acd0e99ef45f382963566
Closes-Bug: #
1443524
Co-Authored-By: Swaminathan Vasudevan <swaminathan.vasudevan@hp.com>
Co-Authored-By: Oleg Bondarev <obondarev@mirantis.com>