Fix launch flags for channel panel

To fix the interaction with the sound picker

Test: launch sound picker from panel, ensure result saved
Test: launch sound picker from panel, cancel
Test: launch more than one panel, make sure all can be edited
Test: change sound from full channel settings page

Fixes: 195739942
Change-Id: I9df86507f8f0cfdd1b0935ca9fe056d24b6d6eac