[Notification] Fix Notification channel Dnd bypass for multiusers

-Permission granted for a given package using shell cmd (user system)
are not sufficient due to a check of notification uid vs packagepreference uid.

-If the packagepreference is deleted then restored, the channel preference
are not taken into account.

Bug: 178032672

Test: CTS/AudioManagerTest

Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: Ia26467f27b31bc048bdb141beac7d764fcb27f51