Added a test for duplicate node_register calls.
Added a test for duplicate node_register calls.

These should throw an error, and they do.

apoorvemohan/haas,kylehogan/hil,henn/hil,meng-sun/hil,SahilTikale/switchHaaS,henn/haas,henn/hil_sahil,henn/hil_sahil,CCI-MOC/haas,kylehogan/hil,henn/hil,lokI8/haas,SahilTikale/haas,meng-sun/hil,kylehogan/haas,apoorvemohan/haas