Fixes #1819572. Do not resurrect the list's selection when the user moved it away.

This is a workaround for a touch mode issue.

Touch mode is propagated lazily to windows. This causes problems in
the following scenario:
- Type something in the AutoCompleteTextView and get some results
- Move down with the d-pad to select an item in the list
- Move up with the d-pad until the selection disappears
- Type more text in the AutoCompleteTextView *using the soft keyboard*
and get new results; you are now in touch mode
- The selection comes back on the first item in the list, even though
the list is supposed to be in touch mode

Using the soft keyboard triggers the touch mode change but that change
is propagated to our window only after the first list layout, therefore
after the list attempts to resurrect the selection.

The trick to work around this issue is to pretend the list is in touch
mode when we know that the selection should not appear, that is when
we know the user moved the selection away from the list.

This boolean is set to true whenever we explicitely hide the list's
selection and reset to false whenver we know the user moved the
selection back to the list.

When this boolean is true, isInTouchMode() returns true, otherwise it
returns super.isInTouchMode().