Show ETA and percentage for disk wipe

So that the operators know better of when disk wipe will end.

Also, only check for the existence of the disk for disk wipe. Checking
stateful partition would prevent us from wiping a partially wiped disk.

BUG=chrome-os-partner:19916
TEST=Wipe a partially wiped disk and see percentage and ETA.

Change-Id: Iff679eea8247b0df6e7353ef26c9626457fc55a1
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/58040
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Jon Salz <jsalz@chromium.org>
1 file changed