DeviceConfig.resetToDefaults is designed to only be used by RescueParty
to reset flags and ban values after a disaster (e.g. bootloop). It's not
designed to be used to clear up local changes and causes CTS tests to
break/be flaky.
Switching to reading existing values, changing them, and reverting
to the pre-existing values to avoid further test breakages.
Bug: 165943447
Test: atest CtsAlarmManagerTestCases
Test: atest CtsBatterySavingTestCases
Test: atest CtsHostsideNetworkTests
Test: atest CtsJobSchedulerTestCases
Test: atest CtsPermissionTestCases:LocationAccessCheckTest
Change-Id: I237d2cd2b862a826f7e871b7a7c31840a3470d0a
b93dd8145e