suzerain: add some check_euler_conserved calls

Includes a new, large radii test case looking
somewhat sane so far.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42722 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: simplify radial_nozzle_cartesian_conserved

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42723 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: extract several subexpressions

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42724 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: rework check_euler_conserved

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42725 0bd85f0b-c151-43b9-a1e9-27231104551f