Log the battery saver changed atom on initialization.

In order for the predicate to be read from the beginning, we need to
ensure the value has some initial state after device reboot
and after logging service starts up.

Bug: 175040249

Test: Manual
Change-Id: Id42f655f3fb42ef3e1ea0cf7bc7b2e536417de7d
Merged-In: Id42f655f3fb42ef3e1ea0cf7bc7b2e536417de7d