fix single select UI behavior on listen tags

[hburgund]

When a uigroup is "select": "single", the UI should enforce that only one uiitem can be in selected state at once. Each time a user selects a uiitem in that uigroup, all other uiitems should be set to unselected, leaving only the most recently selected uiitem in selected state.

Currently, the most recent TWO uiitems are left in selected state each time a new selection is made.

I have changed the Listen Question uigroup on the server to "select": "single" to show this issue. Just open up the Listen tags, tap on the Question tab and then start making selections.