Serialize plurals correctly in neutron xml client

'fixed_ips' and others were incorrectly serialized as dict instead
of arrays

Change-Id: Id50039d158d3f547d72296064a2187fbf90831fe
Closes-Bug: #1255969
Use create_router_interface and create_port

Use create_router_interface and create_port in setUpClass
Correct some typo

Change-Id: I1b4e9a72259e0af5271cfe6caf9a3b16e7ad3938
Merge "Serialize plurals correctly in neutron xml client"
Merge "Use create_router_interface and create_port"