This addition, however, requires some refactoring to be done.  First of
all, to match the best practice we should detach the device prior
resetting it. That's why testVirPCIDeviceDetach is detaching all devices
within 0000:00:01.0 and 0000:00:03.0 range. Then, the brand new test
will reset the 0000:00:02.0 device, so the last testVirPCIDeviceReattach
can reattach all the devices back.

In order to perform a PCI device reset, the dummy config file is not
sufficient anymore and must be replaced with real PCI config (binary
mess). Such config files are to be stored under tests/virpcitestdata/
and ought to have '.config' suffix.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

In the pci_driver_new function it is possible to set a list of
<vendor:device> IDs that the driver knows. These IDs are passed as
variable arguments and are processed  the usual way using va_start() and
va_arg(). However, after all arguments has been processed, we should
call va_end() what we aren't currently doing.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

This commit introduces yet another test under virpcitest:
virPCIDeviceDetach. However, in order to be able to do this, the
virpcimock needs to be extended to model the kernel behavior on PCI
device binding and unbinding (create 'driver' symlinks under the device
tree, check for device ID in driver's ID table, etc.)
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

Among with this test introduce virpcimock as we need to mock some
syscalls, e.g. redirect open() of a file under /sys/bus/pci to a
stub sysfs tree.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>