Fix UiBlcoker regression

We determine if the visibility should be updated by mIsFirstLaunch, and
mIsFirstLaunch is set to false in onStop(). This breaks the updatability
if there's a change before onStop() gets called.

So we move the value assignment to the end of checkUiBlocker() because
at that time, all blocker work should be either finished or timeout.
Also remove mIsFirstLaunch since mUiBlockerFinished can cover the
determination with the new design.

Fixes: 229565193
Test: Toggle Use Location in the location page and see the Recent used
section react accordingly.

Change-Id: Id6005e5b8b29cb8a6309068d0a2177489a3fb2f4