[SC-5134] Make sure externalCatalog is lazy again

## What changes were proposed in this pull request?

I didn't notice the logic conflict in apache@4ac9759 and databricks/runtime@916eb66

This PR just makes `externalCatalog` lazy again.

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <[email protected]>

Closes apache#129 from zsxwing/fix-2.1-build.

Author: zsxwing

sql/core/src/main/scala/org/apache/spark/sql/internal/SharedState.scala

@@ -91,18 +91,17 @@ private[sql] class SharedState(sparkSession: SparkSession) extends Logging {
 
     // Wrap the external catalog with an hook calling external catalog when a
     // catalog hooks object is defined.
-    sparkSession.extensions.buildCatalogHooks(sparkSession) match {
+    val hookedCatalog = sparkSession.extensions.buildCatalogHooks(sparkSession) match {
       case Some(catalogListener) => new HookCallingExternalCatalog(catalog, catalogListener)
       case None => catalog
     }
-  }
 
-  // Create the default database if it doesn't exist.
-  {
+    // Create the default database if it doesn't exist.
     val defaultDbDefinition = CatalogDatabase(
       SessionCatalog.DEFAULT_DATABASE, "default database", warehousePath, Map())
     // Initialize default database if it doesn't already exist
-    externalCatalog.createDatabase(defaultDbDefinition, ignoreIfExists = true)
+    hookedCatalog.createDatabase(defaultDbDefinition, ignoreIfExists = true)
+    hookedCatalog
   }
 
   /**