ZenModePanel: Fix until next alarm missing from do not disturb

Roll only modifies the value of the specified calendar
parameter, causing the until next alarm option to disappear
7 days before each month transition. Use add instead to
move the calendar month and year forward as necessary.

Change-Id: Ic8107af2a8fe71527975c608a12c68dd8a0688a5
Signed-off-by: Evan Anderson <evananderson@aospa.co>