Removed Kafka identity (apache#48)

Author: Gschiavon

core/src/main/scala/org/apache/spark/security/ConfigSecurity.scala

@@ -114,10 +114,6 @@ object ConfigSecurity extends Logging{
             vaultToken,
             SSLConfig.sslTypeDataStore,
             options)
-          case "kafka" => SSLConfig.prepareEnvironment(vaultHost,
-            vaultToken,
-            SSLConfig.sslTypeKafkaStore,
-            options)
           case _ => Map[String, String]()
        }
         secretOptions ++ agg

core/src/main/scala/org/apache/spark/security/SSLConfig.scala

@@ -31,7 +31,6 @@ import org.apache.spark.internal.Logging
 object SSLConfig extends Logging {
 
   val sslTypeDataStore = "DATASTORE"
-  val sslTypeKafkaStore = "KAFKA"
 
   def prepareEnvironment(vaultHost: String,
                          vaultToken: String,