Test apexd behaves correctly when not in fs-checkpoint mode

This CL contains two tests:
1) When fs-checkpoint-mode is false, but fs-rollback-mode is true
2) When both modes are false

Bug: 193648282
Test: atest StagedInstallInternalTest
Change-Id: I9c96296343a7f39a65de9e06e8a07d765f832044
2 files changed