Set trigger for generating the cache info.

Before this change, if artifacts on /system are good so that we only
need to generate the cache info, the trigger is kUnknown. After the
change, the trigger is set to the correct value.

Bug: 271875098
Test: atest odsign_e2e_tests_full
Change-Id: Ib8fecab91f4342ae6975005634b6de49c186c970