test: add flush database in tsim/parser/last_cache.sim and limit1.sim

tests/script/tsim/parser/last_cache.sim

@@ -54,6 +54,7 @@ sql insert into tbd values ("2021-05-11 10:12:29",NULL,NULL,NULL,NULL )
 
 run tsim/parser/last_cache_query.sim
 
+sql flush database $db
 system sh/exec.sh -n dnode1 -s stop -x SIGINT
 
 system sh/exec.sh -n dnode1 -s start

tests/script/tsim/parser/limit1.sim

@@ -55,6 +55,7 @@ print ====== tables created
 run tsim/parser/limit1_tb.sim
 run tsim/parser/limit1_stb.sim
 
+sql flush database $db
 print ================== restart server to commit data into disk
 system sh/exec.sh -n dnode1 -s stop -x SIGINT
 system sh/exec.sh -n dnode1 -s start