fixup devid

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
cli: Keep prompting for required devid/password

These are not optional fields, and skipping them will prevent the token
from being decrypted.  Keep asking the user until they enter something
or hit ^C.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>