Reflected changes of H2O.keySet() in Scala code.

Makefile was failing since h2o-scala was inconsistent due to
changes in h2o core.

h2o-scala/src/main/scala/water/api/dsl/DslLegos.scala

@@ -260,8 +260,8 @@ trait T_H2O_Env[K<:HexKey, VT <: DFrame] { // Operating with only given represen
   def keys(verbose:Boolean = false) = {
     import scala.collection.JavaConversions._ // import implicit inversion for Java collections
     println("*** Available keys *** ")
-    if (H2O.keySet().isEmpty()) println("<None>")
-    else H2O.keySet().foreach((k:Key) => if (k.user_allowed() || verbose) println(k))
+    if (H2O.globalKeySet(null).isEmpty()) println("<None>")
+    else H2O.globalKeySet(null).foreach((k:Key) => if (k.user_allowed() || verbose) println(k))
     println("-----------------------")
   }
   // Access to DKV store is defined by reference