Parallel-proofing Richards exception tests.
Parallel-proofing Richards exception tests.

Fixes #6452

katyhuff/moose,idaholab/moose,andrsd/moose,milljm/moose,SudiptaBiswas/moose,permcody/moose,laagesen/moose,harterj/moose,sapitts/moose,nuclear-wizard/moose,jhbradley/moose,joshua-cogliati-inl/moose,giopastor/moose,laagesen/moose,katyhuff/moose,Chuban/moose,katyhuff/moose,milljm/moose,Chuban/moose,backmari/moose,liuwenf/moose,yipenggao/moose,lindsayad/moose,yipenggao/moose,lindsayad/moose,bwspenc/moose,jessecarterMOOSE/moose,jhbradley/moose,bwspenc/moose,jessecarterMOOSE/moose,bwspenc/moose,dschwen/moose,stimpsonsg/moose,friedmud/moose,giopastor/moose,liuwenf/moose,katyhuff/moose,dschwen/moose,jhbradley/moose,idaholab/moose,SudiptaBiswas/moose,sapitts/moose,SudiptaBiswas/moose,milljm/moose,liuwenf/moose,yipenggao/moose,friedmud/moose,nuclear-wizard/moose,YaqiWang/moose,lindsayad/moose,jhbradley/moose,harterj/moose,YaqiWang/moose,YaqiWang/moose,backmari/moose,andrsd/moose,laagesen/moose,friedmud/moose,SudiptaBiswas/moose,giopastor/moose,idaholab/moose,lindsayad/moose,nuclear-wizard/moose,Chuban/moose,nuclear-wizard/moose,lindsayad/moose,backmari/moose,sapitts/moose,sapitts/moose,backmari/moose,permcody/moose,stimpsonsg/moose,permcody/moose,andrsd/moose,giopastor/moose,harterj/moose,dschwen/moose,friedmud/moose,harterj/moose,liuwenf/moose,stimpsonsg/moose,idaholab/moose,Chuban/moose,jessecarterMOOSE/moose,jasondhales/moose,permcody/moose,joshua-cogliati-inl/moose,dschwen/moose,laagesen/moose,andrsd/moose,sapitts/moose,liuwenf/moose,jessecarterMOOSE/moose,bwspenc/moose,joshua-cogliati-inl/moose,jessecarterMOOSE/moose,YaqiWang/moose,milljm/moose,jasondhales/moose,dschwen/moose,yipenggao/moose,stimpsonsg/moose,liuwenf/moose,jasondhales/moose,andrsd/moose,milljm/moose,bwspenc/moose,joshua-cogliati-inl/moose,jasondhales/moose,harterj/moose,idaholab/moose,SudiptaBiswas/moose,laagesen/moose