Handle and ignore missing information in pci.ids

If Pci_db fails to find the subdevice information for the vGPUs then the
creation of the type is ignored. It is assumed that the config file is either
corrupt or the pci.ids database in the hwdata package is in need of updating.
Merge pull request #1425 from simonjbeaumont/handle-missing-pci-ids

Handle and ignore missing information in pci.ids
Merge pull request #1426 from johnelse/pgpu-fixes

A few fixes for dealing with PGPUs
CP-5842: Blank VGPU.resident_on on VM shutdown

Signed-off-by: John Else <john.else@citrix.com>
CP-5842: Update VGPU.resident_on for passthrough VGPUs

Signed-off-by: John Else <john.else@citrix.com>
Allow starting of VMs without virtual GPUs

Signed-off-by: John Else <john.else@citrix.com>