tests: try to force remove higher minor first

When force removing thin-pool we loose 'real' access to hidden device,
and if such pool is in suspended state, any thin volume cannot be
dropped. It likely should be also checked by dmsetup, but meanwhile
apply simple logic -  try to force remove first all higher minors first
with assumption we first create thin-pool and then thin volume
and there are usually not being released lower dm numbers to
get the order wrong.

test/lib/aux.sh

@@ -419,7 +419,8 @@ teardown_devs_prefixed() {
 		while num_devs=$(dm_table | grep "$prefix" | wc -l) && \
 		    test $num_devs -lt $num_remaining_devs -a $num_devs -ne 0; do
 			test "$stray" -eq 0 || echo "Removing $num_devs stray mapped devices with names beginning with $prefix: "
-			for dm in $(dm_info name --sort open | grep "$prefix") ; do
+                        # HACK: sort also by minors - so we try to close 'possibly later' created device first
+			for dm in $(dm_info name --sort open,-minor | grep "$prefix") ; do
 				dmsetup remove -f "$dm" || true
 			done
 			num_remaining_devs=$num_devs