Deleting VM instance deleted entire scale set from Load Balancer ???

[chsukhija]

Repro Steps

1. Add a VMSS in a Loadbalancer Backend pool.
2. Delete any node that is part of the VMSS
3. The VMSS will get deleted from the Backend pool of LoadBalancer

We were able to reproduce this issues and is similar to #8

[chsukhija]

Deleting a single node will cause VMSS removal from Backend pool