Update VTK-m to get GCC 6.1 compiler fixes

VTK-m + OpenMP + GCC 6.1 + >= O2 caused compile ICE's when
calling functions that had a return value but had no
return statement. This occurs in VTK-m when we have
functions that just throw execptions.

vtk-m @ f2aa6ad5

-Subproject commit f395e084d821265d4ddc782f22c8d9edf8f1f411
+Subproject commit f2aa6ad5be1a97e3fb41ef4680ee2c76c3434ac0