Mock telephony api instead of static flag in CellBroadcastSettings

Bug: 196349924
Test: atest CellBroadcastReceiverOemUnitTests
Test: atest CellBroadcastReceiverUnitTests
Merged-In: I1630d09fca01033a47fb94f07d0b6d8d9c7430c0
Change-Id: I1630d09fca01033a47fb94f07d0b6d8d9c7430c0
(cherry picked from commit 4529cee025dcc67c4dbdaa5411a3106716303772)
3 files changed