[SPARK-4254] [mllib] MovieLensALS bug fix

Changed code so it does not try to serialize Params.
CC: mengxr 	debasish83 srowen

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #3116 from jkbradley/als-bugfix and squashes the following commits:

e575bd8 [Joseph K. Bradley] Merge remote-tracking branch 'upstream/master' into als-bugfix
9401b16 [Joseph K. Bradley] changed implicitPrefs so it is not serialized to fix MovieLensALS example bug

examples/src/main/scala/org/apache/spark/examples/mllib/MovieLensALS.scala

@@ -106,9 +106,11 @@ object MovieLensALS {
 
     Logger.getRootLogger.setLevel(Level.WARN)
 
+    val implicitPrefs = params.implicitPrefs
+
     val ratings = sc.textFile(params.input).map { line =>
       val fields = line.split("::")
-      if (params.implicitPrefs) {
+      if (implicitPrefs) {
         /*
          * MovieLens ratings are on a scale of 1-5:
          * 5: Must see