Fix AddExtraNodeset on distributed meshes
Fix AddExtraNodeset on distributed meshes

This corrects another #1500 bug; in the AddExtraNodeset modifier we
were assuming that every processor has access to every node.
Previously the mesh_modifiers/add_extra_nodeset.test_coord regression
would die when using --distributed-mesh on more than a handful of
processors; now it works for me up to at least 24 processors.

The communication step here is for debugging purposes only, but since
it's debugging user input files rather than MOOSE/libMesh internals,
I'm leaving it enabled in opt mode too.

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