Accessing a subresource that parent does not exist

When accessing a subresource like /nodes/<id>/ports or /chassis/<id>/nodes
where <id> does not exist should fail with 404.

Also fix a typo in the name of a method on test_nodes.py

Change-Id: I5b6beba00fa7cc72b45689c5685914da895b7aa2
Closes-Bug: #1246731
Merge "Accessing a subresource that parent does not exist"