fix failing RCalculator tests

This commit resolves some issues that lingered after 5bd3962.
There were still a few spots in vtkRAdapter where we compensated
for an extra root node.  This is now fixed.  The tree tests in
this module also had to be updated now that VTK trees & R trees
contain the same number of vertices and edges.

Change-Id: I624c6e23b08146f91d3141aded8ccf380d9f6538
Merge topic 'fix_r_tests' into master

ca924e77 fix failing RCalculator tests