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/check/go.py

@@ -1,5 +1,5 @@
-from unit.applications.lang.go import TestApplicationGo
+from unit.applications.lang.go import ApplicationGo
 
 
 def check_go():
-    return TestApplicationGo.prepare_env('empty') is not None
+    return ApplicationGo.prepare_env('empty') is not None