Set "none" scheduler if available (initramfs)

Existing zfs initramfs script logic will attempt to set the 'noop'
scheduler if it's available on the vdev block devices. Newer kernels
have the similar 'none' scheduler on multiqueue devices; this change
alters the initramfs script logic to also attempt to set this scheduler
if it's available.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Garrett Fields <ghfields@gmail.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Colm Buckley <colm@tuatha.org>
Closes #9042