fix drop table on cluster hang

src/Interpreters/DDLWorker.cpp

@@ -727,9 +727,15 @@ void DDLWorker::processTask(DDLTask & task)
                 }
 
                 if (storage && taskShouldBeExecutedOnLeader(rewritten_ast, storage)  && !task.is_circular_replicated)
+                {
                     tryExecuteQueryOnLeaderReplica(task, storage, rewritten_query, task.entry_path, zookeeper);
+                }
                 else
+                {
+                    /// StoragePtr may cause DROP TABLE to hang
+                    storage.reset();
                     tryExecuteQuery(rewritten_query, task, task.execution_status);
+                }
             }
             else
                 tryExecuteQuery(rewritten_query, task, task.execution_status);

tests/queries/0_stateless/01181_db_atomic_drop_on_cluster.reference

+localhost	9000	0		0	0
+localhost	9000	0		0	0
+localhost	9000	0		0	0
+localhost	9000	0		0	0
+localhost	9000	0		0	0

tests/queries/0_stateless/01181_db_atomic_drop_on_cluster.sql

+DROP TABLE IF EXISTS test_repl ON CLUSTER test_shard_localhost SYNC;
+
+CREATE TABLE test_repl ON CLUSTER test_shard_localhost (n UInt64) ENGINE ReplicatedMergeTree('/clickhouse/test_01181/{database}/test_repl','r1') ORDER BY tuple();
+DETACH TABLE test_repl ON CLUSTER test_shard_localhost SYNC;
+ATTACH TABLE test_repl ON CLUSTER test_shard_localhost;
+DROP TABLE test_repl ON CLUSTER test_shard_localhost SYNC;