Bug 1030972 - Import tasks from Bugzilla

@bobsilverberg @Osmose r?
I don't understand why you're doing it this way, as opposed to what's done in the TaskForm [1]. This seems dangerous to not be calling `super`.

[1] https://github.com/mozilla/oneanddone/pull/170/files#diff-cc5e837dd3a3edbf74c31e1cb9480017R305