Start a filesystem checkpoint when committing staged install.

When submitting a staged session for installation, start a filesystem
checkpoint as well. This is a no-op on devices that don't support
filesystem checkpointing.

Bug: 126740531
Test: builds, manually inspect checkpoint state on subsequent boots
Change-Id: I7f73ece143926654628417d0c2384c3d0c1ef754
1 file changed