[SQL]Small bug in unresolved.scala

name should throw exception with name instead of exprId.

Author: Liquan Pei <liquanpei@gmail.com>

Closes #2758 from Ishiihara/SparkSQL-bug and squashes the following commits:

aa36a3b [Liquan Pei] small bug

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/unresolved.scala

@@ -88,7 +88,7 @@ case class Star(
     mapFunction: Attribute => Expression = identity[Attribute])
   extends Attribute with trees.LeafNode[Expression] {
 
-  override def name = throw new UnresolvedException(this, "exprId")
+  override def name = throw new UnresolvedException(this, "name")
   override def exprId = throw new UnresolvedException(this, "exprId")
   override def dataType = throw new UnresolvedException(this, "dataType")
   override def nullable = throw new UnresolvedException(this, "nullable")