Suppress PRE_BOOT notifications for some profiles.

When a profile is unlocked as a side effect of it's parent user being
unlocked, it's confusing to see two sets of identical notifications,
so suppress the set belonging to the profile.

Profile notifications are still shown when the profile has a separate
authentication challenge.

Bug: 29931646
Change-Id: Id8d621451996c9e2f159560894596292ceb00f8d