Fix issue #3381489: IllegalStateException: attempt to re-open...

...an already-closed object: android.database.sqlite.SQLiteQuery

It turns out there is a state we are missing -- the loader is
still needed, but in the inactive list.  In this case the loader
needs to continue holding on to its current data, and not deliver
any new data (which would result in it releasing its old data).

This introduces the new state to Loader, and uses it in
AsyncTaskLoader so all subclasses of that should get the new
correct behavior.

A further improvement would be to unregister CursorLoader's
content listener when going in to this state, but that can
wait for later.

Change-Id: I6d30173b94f8e30b5be31d018accd328cc3388ec