cryptodisk: Fallback to passphrase

cryptodisk: Fallback to passphrase

If a protector is specified, but it fails to unlock the disk, fall back
to asking for the passphrase.

Before requesting the passphrase, the error from the key protector(s)
has to be cleared, or the later code, e.g., LUKS code, may stop as
grub_errno is set. This commit prints error from the key protector(s)
and sets grub_errno to GRUB_ERR_NONE to have a fresh start.

Signed-off-by: Patrick Colp <patrick.colp@oracle.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>