tests: Support changed mkfs.ext2 behavior for -r flag

tests: Support changed mkfs.ext2 behavior for -r flag

Correct nuisance ext234_test failure on newer Linux distros.

Recently, the mkfs.ext2 utility removed support for the -r flag to
specify old (version 0) formats of ext2. A new flag was added to allow
the same behavior. Support both ways of specifying version 0 ext2 file
systems when testing ext2 in GRUB.

Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Glenn Washburn <development@efficientek.com>