Regression: map_anon_nofork test is breaking jenkins on some platforms

This test from the fast_rng branch is breaking jenkins CI in some cases:

17:39:20 util/map_anon_nofork: 
17:39:20   FAIL ../tor/src/test/test_util.c:6206: assert((int)r OP_EQ 1): 0 vs 1
17:39:20   [map_anon_nofork FAILED]

I suspect this is about kernel/header mismatch, but I need to check more closely.

I think we should disable this test in 0.4.0 (since the code is unused) and look for better solutions in 0.4.1.