No way to remove gateway routers

[rajatchopra]

There should be a utility to undo a 'gateway-init' on a node. Specifically useful when nodes are taken out of the clusters.
e.g. the breth0 should be destroyed and eth0 be restored as a regular interface on the host

[alinbalutoiu]

I think this is partially addressed by #298
Leaving that here to make it easier to check the progress for this issue.

[rajatchopra]

@alinbalutoiu Correct. The big portion is done #298. The only remaining step is to remove the actual logical router and ext-switch alongwith the ls-port to join switch.

[shettyg]

This is done now on master.