Join pci_devices when getting all servers in API

The PCI API extension goes back and hits the database for every instance
when getting a list of all instances through the API.  This is causing
problems in testing because it's possible for the instance to be deleted
in between getting the initial list and when the API extension runs.

The API extension really shouldn't be going back to hit the database
anyway, so this patch will resolve that problem.

Change-Id: Id3c8a0b187e399ce2acecd4aaa37ac95e731d46c
Closes-bug: #1270680