Fix the "onPostExecute executed even when cancelled" issue

Renamed onPostExecute to onSuccess and made sure it won't called
if a task is cancelled in time.

Also removed isCancelled().  To implement it right we should make sure
that onPostExecute() isn't finished when setting mCancelled, but it's a bit
of a pain to implement right, and we don't really have to use it.

Change-Id: I3a0baf504506ffc4952a5553f7098a8415842fa3
15 files changed