Merge changes I72aaf4d6,I420cb87c,Iab7c6cf7,Ic4388e20

* changes:
  fs_mgr: overlay: support non-DAP A/B devices
  fs_mgr: overlayfs: test: check for existence of userspace fastboot
  fs_mgr: overlayfs: test: check for ext4 dedupe needing overlay
  fs_mgr: overlayfs: validate that kernel supports scratch filesystem