Make dndMode not lazy

This was causing issues when pressing on the quick toggle in QS, because
the flow being lazy meant that the collection (although technically
SharingStarted.Eagerly) would only start on the first use of the flow -
but since the tile was already expecting a value to have been emitted
then, it was falling back on the initial null value and failing.

Fix: 382497909
Test: reboot device and press quick QS toggle for Modes (without opening
the dialog)
Flag: EXEMPT minor bug fix

Change-Id: Ifada0e05ea6955e23c7ba0acf42a9e489a539f07