address comment

Signed-off-by: Lantao Jin <ltjin@amazon.com>

Author: LantaoJin

opensearch/src/main/java/org/opensearch/sql/opensearch/executor/OpenSearchExecutionEngine.java

@@ -156,8 +156,8 @@ public void explain(
       ResponseListener<ExplainResponse> listener) {
     client.schedule(
         () -> {
-          CalcitePlanContext.isExplain.set(true);
           try {
+            CalcitePlanContext.isExplain.set(true);
             if (format == ExplainFormat.SIMPLE) {
               String logical = RelOptUtil.toString(rel, SqlExplainLevel.NO_ATTRIBUTES);
               listener.onResponse(