loop/010: fix the test output with Bash 5.3

$ ./check loop/010
loop/010 (check stale loop partition)
loop/010 (check stale loop partition)                        [passed]op_device}"
    runtime    ...  93.996s

After the fix:
$ ./check loop/010
loop/010 (check stale loop partition)                        [passed]
    runtime  93.996s  ...  93.797s

Signed-off-by: Yi Zhang <[email protected]>

Author: yizhanglinux

tests/loop/010

@@ -73,8 +73,9 @@ test() {
 	sleep "${TIMEOUT:-90}"
 	{
 		kill -9 $create_pid
+		wait $create_pid
 		kill -9 $detach_pid
-		wait
+		wait $detach_pid
 		sleep 1
 	} 2>/dev/null