This class is not instantiable outside of the package is it does
not leak from NormalizedNodePruner -- therefore it cannot be used
by anyone else. Make sure it's package-private and clean it up
a bit.
JIRA: CONTROLLER-1887
Change-Id: I17911508273d68c2795d38e2156c9407522f55fe Signed-off-by: Robert Varga <robert.varga@pantheon.tech>