set if_not_exists totrue, when creating default db
currently, there are no pre built db in the remote meta backend.
instead,  a "default database" is registered by EACH query node.
To avoid the conflicts of creating the same "default" dataase,
we enable the if_not_exists flag when registering the default db.
@@ -74,7 +74,7 @@ impl MetaStoreCatalog {
};
let plan = CreateDatabasePlan {
- if_not_exists: false,
+ if_not_exists: true,
db: "default".to_string(),
engine: DEFAULT_DB_ENGINE.to_string(),
options: Default::default(),
