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/control.py

@@ -1,6 +1,6 @@
 import json
 
-from unit.http import TestHTTP
+from unit.http import HTTP1
 from unit.option import option
 
 
@@ -29,7 +29,7 @@ def args_handler(conf_func):
     return args_wrapper
 
 
-class TestControl(TestHTTP):
+class Control(HTTP1):
     @args_handler
     def conf(self, conf, url):
         return self.put(**self._get_args(url, conf))['body']