CLOUDSTACK-7372: [vGPU] When a host is put in maintenance mode, vGPU enabled VMs
failed to migrate to the other host in the cluster.

Migration for vGPU VMs is not supported in XS, so instead of migrating them to
new server, stopping them.
CLOUDSTACK-7835: Deleted volumes with null UUID and no removed timestamp in database still appear.
Also removed CREATING -> DESTROY via DESTROYREQUESTED, which was causing the volume to get stuck in expunging
state.
CLOUDSTACK-7421
Unnecessary exception in MS logs while removing default NIC from VM. Following changes are made:
1. Changed the exception from CloudRuntimeException to InvalidParameterValueExecption.
2. Moved out validation logic to UserVMManagerImpl from VirtualMachineManagerImpl.
3. Handling InvalidParameterValueException from async API calls so that they are not logged as ERROR in MS logs.