Create DDL job for create enum command in postprocess as we do for composite types

Since now we don't throw an error for enums that user attempts creating
in temp schema, the preprocess / DDL job that contains the prepared
statement (to idempotently create the enum type) gets executed. As a
result, we were emitting the following warning because of the error the
underlying worker connection throws:

```sql
WARNING:  cannot PREPARE a transaction that has operated on temporary objects
CONTEXT:  while executing command on localhost:xxxxx
WARNING:  connection to the remote node localhost:xxxxx failed with the following error: another command is already in progress
ERROR:  cannot PREPARE a transaction that has operated on temporary objects
CONTEXT:  while executing command on localhost:xxxxx
```

src/backend/distributed/commands/type.c

@@ -260,22 +260,7 @@ PreprocessCreateEnumStmt(Node *node, const char *queryString,
 	/* enforce fully qualified typeName for correct deparsing and lookup */
 	QualifyTreeNode(node);
 
-	/* reconstruct creation statement in a portable fashion */
-	const char *createEnumStmtSql = DeparseCreateEnumStmt(node);
-	createEnumStmtSql = WrapCreateOrReplace(createEnumStmtSql);
-
-	/*
-	 * when we allow propagation within a transaction block we should make sure to only
-	 * allow this in sequential mode
-	 */
-	EnsureSequentialMode(OBJECT_TYPE);
-
-	/* to prevent recursion with mx we disable ddl propagation */
-	List *commands = list_make3(DISABLE_DDL_PROPAGATION,
-								(void *) createEnumStmtSql,
-								ENABLE_DDL_PROPAGATION);
-
-	return NodeDDLTaskList(NON_COORDINATOR_NODES, commands);
+	return NIL;
 }
 
 
@@ -305,9 +290,24 @@ PostprocessCreateEnumStmt(Node *node, const char *queryString)
 		return NIL;
 	}
 
+	/*
+	 * when we allow propagation within a transaction block we should make sure to only
+	 * allow this in sequential mode
+	 */
+	EnsureSequentialMode(OBJECT_TYPE);
+
 	EnsureDependenciesExistOnAllNodes(&typeAddress);
 
-	return NIL;
+	/* reconstruct creation statement in a portable fashion */
+	const char *createEnumStmtSql = DeparseCreateEnumStmt(node);
+	createEnumStmtSql = WrapCreateOrReplace(createEnumStmtSql);
+
+	/* to prevent recursion with mx we disable ddl propagation */
+	List *commands = list_make3(DISABLE_DDL_PROPAGATION,
+								(void *) createEnumStmtSql,
+								ENABLE_DDL_PROPAGATION);
+
+	return NodeDDLTaskList(NON_COORDINATOR_NODES, commands);
 }
 
 

src/test/regress/expected/distributed_types.out

@@ -604,11 +604,6 @@ DETAIL:  "type temp_type" will be created only locally
 CREATE TYPE pg_temp.temp_enum AS ENUM ('one', 'two', 'three');
 WARNING:  "type temp_enum" has dependency on unsupported object "schema pg_temp_xxx"
 DETAIL:  "type temp_enum" will be created only locally
-WARNING:  cannot PREPARE a transaction that has operated on temporary objects
-CONTEXT:  while executing command on localhost:xxxxx
-WARNING:  connection to the remote node localhost:xxxxx failed with the following error: another command is already in progress
-ERROR:  cannot PREPARE a transaction that has operated on temporary objects
-CONTEXT:  while executing command on localhost:xxxxx
 -- clear objects
 SET client_min_messages TO error; -- suppress cascading objects dropping
 DROP SCHEMA type_tests CASCADE;