The pci plugin was only ever merged into the v3 (now v2.1 microversions)
and never the v2 API. Since v2.1 i meant to be identical to v2 it should not
appear in v2 either.
This change disables the pci api functionality in v2.1. It will be renabled
soon after microversions is enabled using a microversion bump.
Related-Bug: 1426241
Partially implements blueprint v2-on-v3-api
Change-Id: Ifc1d6f24d5a637270154b996087a98b41133e014