suzerain: name delta_t_allreducer logger

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43011 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: #2956 WARN on negative delta_t_candidates

This should help reduce the search space for problems like that
encountered in #2956.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43012 0bd85f0b-c151-43b9-a1e9-27231104551f