[livy] Fix LivyConf.contains

Turns out settings.contains checks if the value is in the map, not the
key.

apps/spark/java/livy-core/src/main/scala/com/cloudera/hue/livy/LivyConf.scala

@@ -62,5 +62,5 @@ class LivyConf(loadDefaults: Boolean) {
   def getInt(key: String, default: Int) = getOption(key).map(_.toInt).getOrElse(default)
 
   /** Return if the configuration includes this setting */
-  def contains(key: String): Boolean = settings.contains(key)
+  def contains(key: String): Boolean = settings.containsKey(key)
 }