Fixed that emergency alert dialog not popped up

Fixed by granting START_ACTIVITIES_FROM_BACKGROUND
to the cell broadcast receiver.

Test: Manual
Bug: 130384940

Merged-In: Ie563a8f11ac991ab9568f65df6a4d14eebe47c5e
Change-Id: Ie563a8f11ac991ab9568f65df6a4d14eebe47c5e
(cherry picked from commit 974607aa)