Fix Hive setConf issue

sql/core/src/main/scala/org/apache/spark/sql/SQLConf.scala

@@ -199,8 +199,15 @@ private[sql] class SQLConf extends Serializable {
   /** ********************** SQLConf functionality methods ************ */
 
   /** Set Spark SQL configuration properties. */
-  def setConf(props: Properties): Unit = settings.synchronized {
-    props.foreach { case (k, v) => settings.put(k, v) }
+  def setConf(props: Properties, overwrite: Boolean = true): Unit = settings.synchronized {
+    if (overwrite) {
+      props.foreach { case (k, v) => settings.put(k, v) }  
+    } else {
+      props
+        .filter(p => !settings.containsKey(p._1))
+        .foreach { case (k, v) => settings.put(k, v) }
+    }
+
   }
 
   /** Set the given Spark SQL configuration property. */

sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala

@@ -73,7 +73,7 @@ class SQLContext(@transient val sparkContext: SparkContext)
    *
    * @group config
    */
-  def setConf(props: Properties): Unit = conf.setConf(props)
+  def setConf(props: Properties, overwrite: Boolean = true): Unit = conf.setConf(props, overwrite)
 
   /**
    * Set the given Spark SQL configuration property.

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

@@ -264,7 +264,7 @@ class HiveContext(sc: SparkContext) extends SQLContext(sc) {
     }
 
     protected[hive] lazy val hiveconf: HiveConf = {
-      setConf(sessionState.getConf.getAllProperties)
+      setConf(sessionState.getConf.getAllProperties, false)
       sessionState.getConf
     }