cmake: prefer FindPython2 to FindPython{Interp,Libs}

This is just a better find module and shouldn't have the issues
mentioned in the `smtkConfig.cmake` file.
Status Job ID Name Coverage
  External
passed cdash

passed ghostflow-branch-check-master

failed smtk@master-kerbin-windows-shared-release+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+private+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+python3+remus+vtk

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus+vtk

passed smtk@master-norkit-osx-shared-release+examples+matplotlib

failed smtk@master-praxis-windows-shared-release

failed smtk@master-talosiv-osx-shared-release+examples+matplotlib

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib+private

passed cdash

failed smtk@master-kerbin-windows-shared-release+examples+remus

00:00:53

failed smtk@master-kerbin-windows-shared-release+examples+remus

failed smtk@master-kerbin-windows-shared-release+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+private+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+private+remus

00:03:13

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+private+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+python3+remus+vtk

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+python3+remus+vtk

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+python3+remus+vtk

00:00:05

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus

00:03:12

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus+vtk

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus+vtk

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus+vtk

00:03:11

passed smtk@master-norkit-osx-shared-release+examples+matplotlib

passed smtk@master-norkit-osx-shared-release+examples+matplotlib

00:24:32

passed smtk@master-norkit-osx-shared-release+examples+matplotlib

failed smtk@master-praxis-windows-shared-release

failed smtk@master-praxis-windows-shared-release

00:01:18

failed smtk@master-praxis-windows-shared-release

failed smtk@master-talosiv-osx-shared-release+examples+matplotlib

failed smtk@master-talosiv-osx-shared-release+examples+matplotlib

00:06:52

failed smtk@master-talosiv-osx-shared-release+examples+matplotlib

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib

00:01:00

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib+private

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib+private

00:00:57

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib+private