Detect when encryption failed to complete

For the case there encryption failes to complete because of a kernel
crash or the user power cycling the device, define a flag in the
crypto footer that says encryption is in progress.  Set it when starting
the actual encryption, and clear it when it successfully completes.

When the user is asked for the disk password, if the flag is set,
return a special error to the caller so the UI can know to tell the
user there is no valid data on the disk, and present a button to
wipe and reset the device.

Change-Id: I3723ec77f33437d94b3ac9ad5db0a5c950d11648
2 files changed