[SPARK-19749][SS] Name socket source with a meaningful name

## What changes were proposed in this pull request?

Name socket source with a meaningful name

## How was this patch tested?

Jenkins

Author: uncleGen <hustyugm@gmail.com>

Closes #17082 from uncleGen/SPARK-19749.

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/socket.scala

@@ -46,8 +46,8 @@ object TextSocketSource {
  * support for fault recovery and keeping all of the text read in memory forever.
  */
 class TextSocketSource(host: String, port: Int, includeTimestamp: Boolean, sqlContext: SQLContext)
-  extends Source with Logging
-{
+  extends Source with Logging {
+
   @GuardedBy("this")
   private var socket: Socket = null
 
@@ -168,6 +168,8 @@ class TextSocketSource(host: String, port: Int, includeTimestamp: Boolean, sqlCo
       socket = null
     }
   }
+
+  override def toString: String = s"TextSocketSource[host: $host, port: $port]"
 }
 
 class TextSocketSourceProvider extends StreamSourceProvider with DataSourceRegister with Logging {