ENH: Use TCL_TCLSH versus VTK_TCL_EXE

For tcl tests that do no graphics there is no need to use
VTK_TCL_EXE. TCL_TCLSH works as long as the auto_path is set
corrrectly. This may help solve some timeouts on a few MAC builds.

Change-Id: I209e569af190dd90d78615fec92fb227149dbbc1
Merge topic 'TCLSHReplacesVTK' into master

9b78526a ENH: Use TCL_TCLSH versus VTK_TCL_EXE