Don't corrupt ssd when encrypting and power fails

Stop encryption when battery is low, mark position, and continue on reboot.

Note - support for multiple encrypted volumes removed as no devices seem
to exist with an fstab that uses this feature. If you want support for such
a device, contact me and we will re-add it with appropriate testing.

Bug: 13284213
Change-Id: I1f7178e4f7dd8ea816cbc03ab5c4f6543e98acaa
5 files changed