Unify the *ListDevice API into virnodedeviceobj.c from node_device_driver
and test_driver.  The only real difference between the two is that the test
driver doesn't call the aclfilter API. The name of the new API follows that
of other drivers to "GetNames".

NB: Change some variable names to match what they really are - consistency
with other drivers. Also added a clear of the input names.

This also allows virNodeDeviceObjHasCap to be static to virnodedeviceobj
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>