One can crash dm-flakey by specifying more feature arguments than the
number of features supplied.  Checking for null in arg_name avoids
this.

dmsetup create flakey-test --table "0 66076080 flakey /dev/sdb9 0 0 180 2 drop_writes"
Signed-off-by: NGoldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>