LIU-378 Get node list from api/nodes GET result

[calgray]

When running the translator against a Master Manager instance setup by the run_engine.sh script a key error is appearing on the translator.

This is because the nodes REST API endpoint of the master manager is returning a dictionary:
http://0.0.0.0:8002/api/nodes -> {"nodes": ["172.17.0.4"]}

[awicenec]

There is an error somewhere else and maybe that got lost during one of the merges before. The changes I have committed should actually never result in a list with just a single node and in addition all the nodes in the list should have a port as well. The reason behind that is that we need to be able to specify the port of the DIM and the NM, and with the previous list that was impossible, since it used the first n_island nodes in the list twice, once as a DIM and once as a NM (if the co-locate NM flag was set to True) and attached the default ports in order to access the managers. The updated list thus needs to have at least two entries in the minimal case, one for the DIM and one for the NM, like ['node1:8001', 'node1:8000'] and then this index error would never happen.