tests: cleanup test code

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

test/test_multiports/test_multiports-base-json.py

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

test/test_multiports/test_multiports-base-yaml.py

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

test/test_multiports/test_multiports-invalid-syntax.py

@@ -1,4 +1,3 @@
-import pytest
 import re
 
 

test/test_multiports/test_multiports-merge.py

@@ -1,5 +1,4 @@
 import backoff
-import pytest
 
 
 def test_multiports_and_legacy_configs_should_be_merged(docker_compose, nginxproxy):