[SPARK-20120][SQL] spark-sql support silent mode

## What changes were proposed in this pull request?

It is similar to Hive silent mode, just show the query result. see: [Hive LanguageManual+Cli](https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Cli) and [the implementation of Hive silent mode](https://github.com/apache/hive/blob/release-1.2.1/ql/src/java/org/apache/hadoop/hive/ql/session/SessionState.java#L948-L950).

This PR set the Logger level to `WARN` to get similar result.

## How was this patch tested?

manual tests

![manual test spark sql silent mode](https://cloud.githubusercontent.com/assets/5399861/24390165/989b7780-13b9-11e7-8496-6e68f55757e3.gif)

Author: Yuming Wang <wgyumg@gmail.com>

Closes #17449 from wangyum/SPARK-20120.

sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala

@@ -34,6 +34,7 @@ import org.apache.hadoop.hive.ql.Driver
 import org.apache.hadoop.hive.ql.exec.Utilities
 import org.apache.hadoop.hive.ql.processors._
 import org.apache.hadoop.hive.ql.session.SessionState
+import org.apache.log4j.{Level, Logger}
 import org.apache.thrift.transport.TSocket
 
 import org.apache.spark.internal.Logging
@@ -275,6 +276,10 @@ private[hive] class SparkSQLCLIDriver extends CliDriver with Logging {
 
   private val console = new SessionState.LogHelper(LOG)
 
+  if (sessionState.getIsSilent) {
+    Logger.getRootLogger.setLevel(Level.WARN)
+  }
+
   private val isRemoteMode = {
     SparkSQLCLIDriver.isRemoteMode(sessionState)
   }