Update HiveMetastoreCatalog.scala

I think it's better to defined hiveQlTable as a val

Author: baishuo

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala

@@ -258,7 +258,7 @@ private[hive] case class MetastoreRelation
   // org.apache.hadoop.hive.ql.metadata.Partition will cause a NotSerializableException
   // which indicates the SerDe we used is not Serializable.
 
-  def hiveQlTable = new Table(table)
+  val hiveQlTable = new Table(table)
 
   def hiveQlPartitions = partitions.map { p =>
     new Partition(hiveQlTable, p)