xenserver: Completely ignore datapath devices for renaming purposes.

xenserver: Completely ignore datapath devices for renaming purposes.

Commit 2bb451b69 "xenserver: Rename network devices to match MAC addresses
of physical PIFs" started renaming network devices so that they match
the MAC address that we expect them to have.  This worked OK at the time.

Commit 35c979bff "vswitchd: Support creating fake bond device interfaces"
later started creating fake bond devices to make the Citrix QA scripts
happier.

Unfortunately these commits interact badly: the bond devices created by
the latter commit are sometimes chosen as the physical devices to be
renamed over the physical PIF device names.  This is because we do allow
datapath internal ports to be chosen as "physical devices" as a last
resort.  This commit reverses this decision, eliminating that possibility.
This probably won't become a problem unless somehow we encounter a physical
Ethernet card driver that lacks a queue, but that is unlikely since the
performance would be awful.