[SPARK-16959][SQL] Rebuild Table Comment when Retrieving Metadata from Hive Metastore

### What changes were proposed in this pull request?
The `comment` in `CatalogTable` returned from Hive is always empty. We store it in the table property when creating a table. However, when we try to retrieve the table metadata from Hive metastore, we do not rebuild it. The `comment` is always empty.

This PR is to fix the issue.

### How was this patch tested?
Fixed the test case to verify the change.

Author: gatorsmile <gatorsmile@gmail.com>

Closes #14550 from gatorsmile/tableComment.

sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveClientImpl.scala

@@ -413,7 +413,8 @@ private[hive] class HiveClientImpl(
           properties = Option(h.getTTable.getSd.getSerdeInfo.getParameters)
             .map(_.asScala.toMap).orNull
         ),
-        properties = properties,
+        properties = properties.filter(kv => kv._1 != "comment"),
+        comment = properties.get("comment"),
         viewOriginalText = Option(h.getViewOriginalText),
         viewText = Option(h.getViewExpandedText),
         unsupportedFeatures = unsupportedFeatures)

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveDDLSuite.scala

@@ -135,8 +135,11 @@ class HiveDDLSuite
         sql(s"CREATE VIEW $viewName COMMENT 'no comment' AS SELECT * FROM $tabName")
         val tableMetadata = catalog.getTableMetadata(TableIdentifier(tabName, Some("default")))
         val viewMetadata = catalog.getTableMetadata(TableIdentifier(viewName, Some("default")))
-        assert(tableMetadata.properties.get("comment") == Option("BLABLA"))
-        assert(viewMetadata.properties.get("comment") == Option("no comment"))
+        assert(tableMetadata.comment == Option("BLABLA"))
+        assert(viewMetadata.comment == Option("no comment"))
+        // Ensure that `comment` is removed from the table property
+        assert(tableMetadata.properties.get("comment").isEmpty)
+        assert(viewMetadata.properties.get("comment").isEmpty)
       }
     }
   }