Test can't work because it requires ImportFiles2 functionality which python submitted requests don't get currently.
PUB-923: Fix K-Means to pass golden R test.

Problem: within_cluster_variances was computed correctly, but the name was
wrong, since the R wrapper equates this value with withinss, which is the
within_cluster_sum_of_squares. So in order to not upset the R side of things,
we compute sum of squares instead of variances.

Also re-enable returning total_within_SS from R.
Merge branch 'master' of https://github.com/0xdata/h2o