tests: cleanup test code

- remove unused imports in test cases
- fix code smells and code style in conftest.py

test/test_virtual-path/test_custom_conf.py

@@ -1,5 +1,6 @@
 import pytest
 
+
 def test_default_root_response(docker_compose, nginxproxy):
     r = nginxproxy.get("http://nginx-proxy.test/")
     assert r.status_code == 418