Only add preconditioners after field splits
Only add preconditioners after field splits

Otherwise FieldSplitPreconditioner gets terribly confused.

This will hopefully fix the failing regression test in #8674

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