Replace remaining print statements with print function

Replace remaining print statements with print function

Also add the appropriate __future__ import statement.

Signed-off-by: Julien Goodwin <jgoodwin@studio442.com.au>
[rlb@defaultvalue.org: memtest-cmd.py: remove a few preexisting
 trailing spaces that were carried over; adjust commit summary]
Reviewed-by: Rob Browning <rlb@defaultvalue.org>
Tested-by: Rob Browning <rlb@defaultvalue.org>