Use OS::Nova::Server for NeutronResourcesTestJSON

This is part of an ongoing effort to ensure there are no references to AWS::
resources in tempest.api or tempest.scenario

Partial-Bug: #1187942

Change-Id: I11ce6b164b6fb5507ee95a6b416dbe5d3352c77e
Merge "Use OS::Nova::Server for NeutronResourcesTestJSON"