only instantiate a new route if it differs, refs #976

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@16620 29f149b2-0c63-11e1-8f5c-a347f6a9acd0
adapting tests to new rerouting, refs #21, #976

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@16621 29f149b2-0c63-11e1-8f5c-a347f6a9acd0