utils.appcall(), too, must abort before closing the connection, just in case

something went wrong during execution of 'function'.

lib/python/Testing/ZopeTestCase/utils.py

@@ -147,6 +147,7 @@ def appcall(function, *args, **kw):
     try:
         return function(*args, **kw)
     finally:
+        transaction.abort()
         close(app)