caddy-frontend/test: fix snapshot in error cases

Because we were simply using "setupClass", all classes where storing
snapshots in the same folder, so if more than one class failed we also
had an error in storing snapshot.

/reviewed-on nexedi/slapos!683

software/caddy-frontend/test/test.py

@@ -534,7 +534,7 @@ class SlaveHttpFrontendTestCase(SlapOSInstanceTestCase):
       cls.startServerProcess()
     except BaseException:
       cls.logger.exception("Error during setUpClass")
-      cls._cleanup('setUpClass')
+      cls._cleanup("{}.{}.setUpClass".format(cls.__module__, cls.__name__))
       cls.setUp = lambda self: self.fail('Setup Class failed.')
       raise
 
@@ -559,7 +559,9 @@ class SlaveHttpFrontendTestCase(SlapOSInstanceTestCase):
       cls.waitForCaddy()
     except BaseException:
       cls.logger.exception("Error during setUpClass")
-      cls._cleanup('setUpClass')
+      # "{}.{}.setUpClass".format(cls.__module__, cls.__name__) is already used by SlapOSInstanceTestCase.setUpClass
+      # so we use another name for snapshot, to make sure we don't store another snapshot in same directory.
+      cls._cleanup("{}.SlaveHttpFrontendTestCase.{}.setUpClass".format(cls.__module__, cls.__name__))
       cls.setUp = lambda self: self.fail('Setup Class failed.')
       raise