pciSharesBusWithActive fails to find multiple devices on bus

pciSharesBusWithActive fails to find multiple devices on bus

The first conditional is always true which means the iterator will
never find another device on the same bus.

    if (dev->domain != check->domain ||
        dev->bus != check->bus ||
  ----> (check->slot == check->slot &&
         check->function == check->function)) <-----

The goal of that check is to verify that the device is either:

  in a different pci domain
  on a different bus
  is the same identical device

This means libvirt may issue a secondary bus reset when there are
devices
on that bus that actively in use by the host or another guest.

* src/util/pci.c: fix a bogus test in pciSharesBusWithActive()