Clean up the code that deletes snapshots by inode (1/n)

Per b/147806409, the old code to delete snapshots by inode didn't work.
There is no point in storing mCeSnapshotInodes inside
PackageRollbackInfo. Let's remove related code.

TODO: fix ApexManager/Installer APIs that have unused parameter/return
values.

Bug: 154897348
Test: atest RollbackStoreTest RollbackUnitTest AppDataRollbackHelperTest

Change-Id: I66357c22607bfffbe4d9f55fc13c4c657d5f700c