Fix VM.allowed_operations for VMs with VGPUs

Block migrate/suspend/checkpoint for VMs with any kind of VGPU (not just
for VMs with passthrough VGPUs).

Signed-off-by: John Else <john.else@citrix.com>
Block migrate_send for VMs with attached PCIs

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #1453 from johnelse/vgpu-vm-allowed-ops

Fix VM.allowed_operations for VMs with VGPUs