[WAL-2333] Fix attaching subnets to existing VM.
[WAL-2333] Fix attaching subnets to existing VM.

opennode/waldur-mastermind,opennode/waldur-mastermind,opennode/nodeconductor-assembly-waldur,opennode/waldur-mastermind,opennode/nodeconductor-assembly-waldur,opennode/waldur-mastermind,opennode/nodeconductor-assembly-waldur