* include/libvirt/virterror.h src/virterror.c: if a driver's virInterfaceLookupByMACString() function finds more than one interface with the desired MAC Address, this new error is raised.
* include/libvirt/virterror.h src/virterror.c: if a driver's virInterfaceLookupByMACString() function finds more than one interface with the desired MAC Address, this new error is raised.