K-means test fails under clang

[zmughal]

Fails on this line:

is(tapprox( t_kmeans_bad(), 0 ), 1);

https://rt.cpan.org/Public/Bug/Display.html?id=96742 also had a similar bug.

[mohawk2]

The test has been finagled to be deterministic by changing random_cluster to use Primitive::random and using srandom in the test. The CI for MacOS will be using clang, and that shows no problems. Therefore, this is no longer an issue.