Move #addToken and #hasToken into Rollback (2/n)

Move some methods from NewRollback into Rollack. By reducing the
difference b/t NewRollback and Rollback, it will be easier to merge
them later.

Bug: 147400979
Test: atest RollbackTest
Change-Id: I248f26345cc4070a932909a492d71e5940ed8e66