Cycles Hair: Corrected own stochastic hair rng mistake and removed an unnecessary padding variable

- Corrected the Sobol dimension and removed a pad variable in Curve Struct.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56108 954f8c5b-7b00-dc11-b283-0030488c597c