fix: unstable test case

tests/script/tsim/valgrind/checkError3.sim

@@ -62,7 +62,14 @@ system sh/exec.sh -n dnode1 -s stop -x SIGINT
 system sh/exec.sh -n dnode1 -s start -v
 
 print =============== stepa: query data
-sql select * from c1
+steps: 
+	$x = $x + 1
+	sleep 1000
+	if $x == 20 then
+		return -1
+	endi
+sql select * from c1 -x steps
+
 sql select * from stb
 sql select * from stb_1
 sql select ts, c1, c2, c3 from c1

tests/script/tsim/valgrind/checkError6.sim

@@ -158,9 +158,14 @@ print =============== restart
 system sh/exec.sh -n dnode1 -s stop -x SIGINT
 system sh/exec.sh -n dnode1 -s start -v
 
-sleep 1000
+steps: 
+	$x = $x + 1
+	sleep 1000
+	if $x == 20 then
+		return -1
+	endi
+sql select avg(tbcol) as c from stb -x steps
 
-sql select avg(tbcol) as c from stb
 sql select avg(tbcol) as c from stb where ts <= 1601481840000
 sql select avg(tbcol) as c from stb where tgcol < 5 and ts <= 1601481840000
 sql select avg(tbcol) as c from stb interval(1m)