Fix for underscore to dash conversion

DHCP OMAPI normally uses dashes as a separator for field words. Python does not accept dashes in kwarg keys, so there is a conversion in the __lookup function to convert _ to -. However, there seems to be a bug that prevents that conversion to be actually used for some parameters.

pypureomapi.py

@@ -1214,7 +1214,7 @@ def __lookup(self, ltype, **kwargs):
 			elif _k == "name":
 				msg.obj.append((b"name", kwargs[k].encode('utf-8')))
 			else:
-				msg.obj.append((str(k).encode(), kwargs[k].encode('utf-8')))
+				msg.obj.append((str(_k).encode(), kwargs[k].encode('utf-8')))
 		response = self.query_server(msg)
 		if response.opcode != OMAPI_OP_UPDATE:
 			raise OmapiErrorNotFound()