Catch an additional networking case when attempting to detect wedges.

wedge/local/share/check_mk/agents/special/agent_triton_wedge

@@ -63,8 +63,9 @@ async def async_connect(src, dest):
             # If we hit here, a packet might have been lost, so try again.
             pass
         except OSError as e:
-            if e.errno == errno.EHOSTUNREACH:
+            if e.errno == errno.EHOSTUNREACH or e.errno == errno.ENETUNREACH:
-                # If there is no route, no point retrying either.
+                # If there is no route, or we're dealing with firewall,
+                # no point retrying either.
                 break
             else:
                 raise