Investigate possible problem with SsaTestCase 00003

[artgoldberg]

SsaTestCase 00003 fails intermittently, when all other tests pass and only one other test runs more than once. Temporarily, I have increased the # of simulation runs used by SsaTestCase 00003 by a factor of 10. See commit 1a675b53.

E.g., in https://circleci.com/gh/KarrLab/wc_sim/1967 produces:

----------------------------- Captured stdout call -----------------------------
Verifying DISCRETE_STOCHASTIC case 00001
starting run 1 of 20 of model test_case_00001
starting run 2 of 20 of model test_case_00001
starting run 4 of 20 of model test_case_00001
starting run 8 of 20 of model test_case_00001
starting run 16 of 20 of model test_case_00001
Verifying DISCRETE_STOCHASTIC case 00003
starting run 1 of 20 of model test_case_00003
starting run 2 of 20 of model test_case_00003
starting run 4 of 20 of model test_case_00003
starting run 8 of 20 of model test_case_00003
starting run 16 of 20 of model test_case_00003
starting run 1 of 20 of model test_case_00003
starting run 2 of 20 of model test_case_00003
starting run 4 of 20 of model test_case_00003
starting run 8 of 20 of model test_case_00003
starting run 16 of 20 of model test_case_00003
starting run 1 of 20 of model test_case_00003
starting run 2 of 20 of model test_case_00003
starting run 4 of 20 of model test_case_00003
starting run 8 of 20 of model test_case_00003
starting run 16 of 20 of model test_case_00003
Verifying DISCRETE_STOCHASTIC case 00004
starting run 1 of 20 of model test_case_00004
starting run 2 of 20 of model test_case_00004
starting run 4 of 20 of model test_case_00004
starting run 8 of 20 of model test_case_00004
starting run 16 of 20 of model test_case_00004