Switch to exceptions for most cp calls

This switches the checkpoint calls that don't need to return a value
to return 0 on success, and an error on failure. This will be transalted
to exceptions for java binder users. needsCheckpoint and needsRollback
still return a boolean value.

Test: vdc setCheckpoint 2 then reboot 3 times checking state
Bug: 112901762
Change-Id: Idd3b5e6036631562a86d5123f533b86cf3bd6032
Merged-In: Idd3b5e6036631562a86d5123f533b86cf3bd6032
6 files changed