Fix DataSaverBackend objects created on background threads

Add the main looper to the handler created with each
DataSaverBackend to avoid crashes when the objects are
created on background threads.

Bug: 62022517
Test: make RunSettingsRoboTests
Change-Id: I7396107e4ed06982c8cd300912ce1f4e3c63df4c
Merged-In: Ie5ffabbfbe7660761527b3ecd51e6bc5a43c1ace
2 files changed