Add landing page test to the basic test set (#3928)

We check that landing page is working when the network is down but we don't
check it in the happy path. Add its test to make it more obvious when the
just landing page is broken.

tests/smoke_test/test_basic.py

@@ -65,6 +65,12 @@ def test_supervisor_logs(shell):
     _LOGGER.info("%s", "\n".join(output))
 
 
+@pytest.mark.dependency(depends=["test_init"])
+def test_landing_page(shell):
+    web_index = shell.run_check("curl http://localhost:8123")
+    assert "</html>" in " ".join(web_index)
+
+
 def test_systemctl_status(shell):
     output = shell.run_check("systemctl --no-pager -l status -a || true")
     _LOGGER.info("%s", "\n".join(output))