tests: cleanup test code

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

test/test_host-network-mode/test_host-network-mode.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_forwards_to_bridge_network_container(docker_compose, nginxproxy):
     r = nginxproxy.get("http://bridge-network.nginx-proxy.tld/port")
     assert r.status_code == 200   

test/test_host-network-mode/test_proxy-host-network-mode.py

@@ -1,6 +1,3 @@
-import pytest
-
-
 def test_forwards_to_host_network_container_1(docker_compose, nginxproxy):
     r = nginxproxy.get("http://host-network-1.nginx-proxy.tld:8888/port")
     assert r.status_code == 200