test: Make net tests depend on CONFIG_CMD_NET

This fails on samus_tpl as there is no 'net' command.

   => net list
   Unknown command 'net' - try 'help' !

Fix it by adding a condition for the test.

Add a blank line to keep pylint happy.

Signed-off-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_net.py

@@ -91,6 +91,8 @@ env__router_on_net = True
 net_set_up = False
 net6_set_up = False
 
+
+@pytest.mark.buildconfigspec('cmd_net')
 def test_net_pre_commands(ubman):
     """Execute any commands required to enable network hardware.