Some tests for MH fail for certain random seeds

[torfjelde]

Ref: #1567 (comment)

This is where the failure happens: https://github.com/TuringLang/Turing.jl/blob/master/test/inference/mh.jl#L149-L152
In particular v2 can sometimes be 0 (i.e. all samples are rejected).

[yebai]

Likely fixed by recent bumps to number of MCMC samples.