[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

(cherry picked from commit c315d1316cb2372e90ae3a12f72d5b3304435a6b)
Signed-off-by: Xiangrui Meng <meng@databricks.com>