check: improve test list randomization

awk doesn't have a particularly good random number generator -- it seeds
from the Unix epoch time in seconds, which means that the run order
across a bunch of VMs started at exactly the same time are unsettlingly
predictable.  Therefore, at least try to seed it with bash's $RANDOM,
which is slightly less predictable.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

check

@@ -242,13 +242,13 @@ _prepare_test_list()
 	done
 
 	# sort the list of tests into numeric order
-	list=`sort -n $tmp.list | uniq`
-	rm -f $tmp.list
-
-	if $randomize
-	then
-		list=`echo $list | awk -f randomize.awk`
+	if $randomize; then
+		sorter="awk -v seed=$RANDOM -f randomize.awk"
+	else
+		sorter="cat"
 	fi
+	list=`sort -n $tmp.list | uniq | $sorter`
+	rm -f $tmp.list
 }
 
 # Process command arguments first.