DVR l3 agent should check for snat namespace existence before adding or deleting anything from the namespace

[Swaminathan Vasudevan]

Check for snat_namespace existence in the node before any operation
in the namespace.

Today we check the self.snatnamespace which may or may not reflect
the exact state of the system.

If the snat_namespace is accidentally deleted and if we try to
remove the gateway from the router, the agent throws in a bunch of
error messages and the agent goes in loop constantly spewing error
messages.

Here is the link to the error message.

http://paste.openstack.org/show/492700/

This can be easily reproduced.

1. Create a network
2. Create a subnet
3. Create a router ( dvr)
4. Attach the subnet to the router.
5. Configure default gateway to the router.
6. Now verify the namespaces in the 'dvr_snat' node.
7. You should see
    a. snat_namespace
    b. router_namespace
    c. dhcp namespace.
8. Now delete the snat_namespace.
9. Try to remove the gateway from the router.
10. Watch the L3 agent logs

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/300358

[Brian Haley (brian-haley)]

I think this was all fixed by https://review.openstack.org/#/c/326729/ so can probably abandon patch and close this bug.

[Swaminathan Vasudevan (swaminathan-vasudevan)]

Yes you are right, we can close this bug, since multiple fixes to address in this area have already merged.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Swaminathan Vasudevan (<email address hidden>) on branch: master
Review: https://review.openstack.org/300358
Reason: Multiple patches that addressed the issues with this bug have already merged. So will adbandon this patch and close this bug.

[Swaminathan Vasudevan (swaminathan-vasudevan)]

This bug can be closed, since alternate patches have merged upstream that addressed the same problem.