restart_and_restore.inc does not pass --innodb-undo-tablespaces to --copy-back

We should run all of --suite=mariabackup tests with at least two different combinations for innodb_undo_tablespaces. The default value is 0.

A major problem is that the restore tests always invoke --copy-back without an innodb_undo_tablespaces parameter. I tested both by invoking

./mtr --mysqld=--innodb-undo-tablespaces=3 --suite=mariabackup

and by creating an .opt file with the parameter in it.
Backup does get the parameter right, maybe also prepare does get it.