suzerain: add init_wall call

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42309 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: trace of grad_m for div_m

Moves the computation down to where it is needed.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42310 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: collocate u- and tau-related computations

Hopefully slightly-better locality.  Simpler mucking with
results for testing purposes in #2983.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42311 0bd85f0b-c151-43b9-a1e9-27231104551f