Hooks fail, log produced when running async_task with method

[roharvey]

This is a duplicate of #613, which was closed without a fix.

Running async_task (in async mode) passing in a method argument (e.g. self.run) causes a problem after the function has finished, before the hook is run. This also produces an error log. The same problem doesn't occur when running in sync mode, so if you develop with Q_CLUSTER["sync"] = True, you will avoid the issue.