Removed "NT_" prefix in network topology tables

Normalized table names in network topology. Files that have been modified:

openstack_dashboard/dashboards/project/network_topology/instances/
tables.py
openstack_dashboard/dashboards/project/network_topology/ports/
tables.py
openstack_dashboard/dashboards/project/network_topology/routers/
tables.py

Change-Id: I60895fd1872f7026ceb5c027c1346343e241d47b
Closes-Bug: #1254484
Merge "Removed "NT_" prefix in network topology tables"