Fix issue with updated cell labels.

Updating the visible cell in the table is not a sustainable solution as it gets
rerendered by leaving the view via scrolling and thus the text would revert. It
was also possible to update the text in the wrong cell by shifting the topmost
cell off the screen and then editing. This udpates the default text on the
renderer and then re-renders the cell based on indexpath thus ensuring the
proper cell text changes and remains changed.