quick patch to address bad handling of timeout response

Author: siddacious

adafruit_wiznet5k/adafruit_wiznet5k_dhcp.py

@@ -288,7 +288,11 @@ def request_dhcp_lease(self):
                                        ((time.monotonic() - start_time) / 1000))
                 self._dhcp_state = STATE_DHCP_DISCOVER
             elif self._dhcp_state == STATE_DHCP_DISCOVER:
-                msg_type, xid = self.parse_dhcp_response(self._timeout)
+                resp = self.parse_dhcp_response(self._timeout)
+                if resp == 255:
+                    print("Timeout waiting for DHCP response")
+                    continue
+                msg_type, xid  = resp
                 if msg_type == DHCP_OFFER:
                     # use the _transaction_id the offer returned,
                     # rather than the current one