9b225ac307 has been causing GraphX tests
to fail nondeterministically, which is blocking development for others.
Author: Ankur Dave <ankurdave@gmail.com>
Closes#2271 from ankurdave/SPARK-3400 and squashes the following commits:
10c2a97 [Ankur Dave] [HOTFIX] [SPARK-3400] Revert 9b225ac "fix GraphX EdgeRDD zipPartitions"
00362dac97