Add fs_mgr support for dm-verity modes

Add support for dm-verity modes and storing persistent state in
a location specified by the following properties:

  ro.verity.state.location
  ro.verity.state.offset

If these properties do not exist, dm-verity is always loaded in
EIO mode. If the properties do exist, but the location does not
have valid state data, dm-verity is loaded in RESTART mode. The
mode is updated to LOGGING if a dm-verity triggered restart has
occurred.

Change-Id: Ibb82953594d234f81ad21c40f524190b88e4ac8f