poll umount completion from /proc/mounts

- umount operation is asynchronous except for root partition.
  Returning from umount does not guarantee completion of
  umount. Poll /proc/mounts to confirm completion of umount.
- Treat all devices mounting to /data as emulated devices. This is
  future proof when fs other than sdcardfs is used.
- Drop quota sync from sync step. There is no differences in
  frequencies of quota error.
- Run umount in reverse order from mounting order so that any
  hidden dependency can be auto-resolved.
- Add dump of lsof and /proc/mounts when umount fails. lsof only runs
  when selinux is toggled into permissive mode. The dump is enabled
  only for non-user build.
- Keep logcat until vold shutdown in case vold has any error to report.

bug: 36551218
Test: python packages/services/Car/tools/bootanalyze/bootanalyze.py -r -c packages/services/Car/tools/bootanalyze/config.yaml -n 1000 -f -e 20 -w 30

Change-Id: I87b17b966d7004c205452d81460b02c6acf50d45