[SPARK-7678] [ML] Fix default random seed in HasSeed

Changed shared param HasSeed to have default based on hashCode of class name, instead of random number.
Also, removed fixed random seeds from Word2Vec and ALS.

CC: mengxr

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

Closes #6251 from jkbradley/scala-fixed-seed and squashes the following commits:

0e37184 [Joseph K. Bradley] Fixed Word2VecSuite, ALSSuite in spark.ml to use original fixed random seeds
678ec3a [Joseph K. Bradley] Removed fixed random seeds from Word2Vec and ALS. Changed shared param HasSeed to have default based on hashCode of class name, instead of random number.