Tests: get rid of classes in test files.

Class usage came from the unittest framework and it was always redundant
after migration to the pytest.  This commit removes classes from files
containing tests to make them more readable and understandable.

test/unit/http.py

@@ -10,7 +10,7 @@ import pytest
 from unit.option import option
 
 
-class TestHTTP:
+class HTTP1:
     def http(self, start_str, **kwargs):
         sock_type = kwargs.get('sock_type', 'ipv4')
         port = kwargs.get('port', 7080)