Automatically set pc_hypre_boomeramg_strong_threshold to 0.7 for 3D meshes
closes #3245
Override the automatic adjustment of the strong threshold few a few sensitive tests
Merge pull request #3630 from permcody/hypre_threshold_3245

Automatically set pc_hypre_boomeramg_strong_threshold to 0.7 for 3D mesh...
Merge commit '80480a7cfe3cfc6de7d17ca57d2a46be27619879'