Optionally append managed service approvals

If the backup comes from a pre O device, don't wipe
preexisting managed service grants (which were introduced in O).


Merged-In: I142df7acb11309bc4f5f185e45a1f91f86d0334a
Merged-In: Ie569972dc0d076718a3a9c59e1ebd942c5bfa987
Test: manual, restore from N to O DR
Bug: 64232609
Change-Id: Ieec2c821d9a088c69a5bc143acf8537ba300202d