Bug#944054: statsmodels: ignored test failures on at least ppc64el

[Rebecca N. Palmer]

Control: severity -1 important
(mostly for ignoring failures, not the actual ones that happened)

After further testing, it looks like 
base.tests.test_penalized.TestPenalizedPoissonOraclePenalized2* is on a 
convergence edge: if the random seed isn't fixed, it sometimes finds all 
4 and sometimes 3 on both amd64 and qemu-ppc64el.

Hence, I intend to mark this xfail.