Fixup call to changed option in PETSc version.
Fixup call to changed option in PETSc version.

Also silence comparison warning.
refs #8805

nuclear-wizard/moose,milljm/moose,lindsayad/moose,milljm/moose,idaholab/moose,milljm/moose,liuwenf/moose,harterj/moose,harterj/moose,liuwenf/moose,harterj/moose,idaholab/moose,bwspenc/moose,sapitts/moose,sapitts/moose,bwspenc/moose,lindsayad/moose,SudiptaBiswas/moose,andrsd/moose,bwspenc/moose,Chuban/moose,liuwenf/moose,yipenggao/moose,permcody/moose,permcody/moose,harterj/moose,milljm/moose,sapitts/moose,bwspenc/moose,nuclear-wizard/moose,YaqiWang/moose,yipenggao/moose,liuwenf/moose,dschwen/moose,dschwen/moose,jessecarterMOOSE/moose,andrsd/moose,Chuban/moose,liuwenf/moose,milljm/moose,sapitts/moose,SudiptaBiswas/moose,yipenggao/moose,dschwen/moose,nuclear-wizard/moose,lindsayad/moose,andrsd/moose,jessecarterMOOSE/moose,permcody/moose,andrsd/moose,idaholab/moose,laagesen/moose,jessecarterMOOSE/moose,lindsayad/moose,friedmud/moose,sapitts/moose,laagesen/moose,Chuban/moose,idaholab/moose,permcody/moose,Chuban/moose,dschwen/moose,jessecarterMOOSE/moose,friedmud/moose,nuclear-wizard/moose,laagesen/moose,friedmud/moose,yipenggao/moose,laagesen/moose,SudiptaBiswas/moose,YaqiWang/moose,YaqiWang/moose,andrsd/moose,liuwenf/moose,laagesen/moose,harterj/moose,idaholab/moose,bwspenc/moose,SudiptaBiswas/moose,SudiptaBiswas/moose,dschwen/moose,lindsayad/moose,YaqiWang/moose,friedmud/moose,jessecarterMOOSE/moose