This has been hardcoded to "false" since 2.10.0, since secrets required
to unlock block devices are now always provided up front instead of using
interactive prompts.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>