skip variables when enumerating registry entries

closes: #2733
test interface type identification function

see: #2733
consider 0x1 as ethernet type

Actually, it means 'unspecified', as this is the value returned
by OID_GEN_PHYSICAL_MEDIUM plus 1:
 1 => NdisPhysicalMediumUnspecified
 2 => NdisPhysicalMediumWirelessLan
more explicit function name