Update show system experiment behavior.

When the experiment flag is flipped to on, toggle the "show system
accesses" setting to on one time and then do not modify the value again
unless the experiment is turned off and then on again.

Bug: 191503437
Test: atest LocationControllerImplTest
Change-Id: I25e647bc3ccfb911719b2047a5096f9a9e62a3ad