Fix a bug with the settings for skipping integrity check for verifiers.

Currently we read it at the start and cache it. This will cause any change in
settings to have effect only after restart. This is probably not what we want.

Bug: 150220476
Test: atest AppIntegrityManagerServiceImplTest
Change-Id: Icf4fc0e83e3563544b022c722e893a98f3512f25