gw_port should be set as lazy='join'

This forces the object to be ready ahead of accessing time.
The change in loading behavior is also beneficial while listing
routers, as reduces the amount of queries being issued. Tests
show a performance gain of 15-30% for router-list times.

As Mr. Aaron Rosen is used to saying: Woot woot!!

Closes-bug: #1309144

Change-Id: Ibae261b91de26ca7c50e3f6c80e9be2a799785a3
ML2 Cisco Nexus MD: Improve Unit Test Coverage

Improve unit test coverage for:
neutron/plugins/ml2/drivers/cisco/ modules.

Current coverage info:
neutron/plugins/ml2/drivers/cisco/nexus/nexus_models_v2      65%
neutron/plugins/ml2/drivers/cisco/nexus/nexus_network_driver 82%
neutron/plugins/ml2/drivers/cisco/nexus/credentials_v2       81%
neutron/plugins/ml2/drivers/cisco/nexus/mech_cisco_nexus     78%
neutron/plugins/ml2/drivers/cisco/nexus/config               75%

With these updates:
neutron/plugins/ml2/drivers/cisco/nexus/mech_cisco_nexus     99%
neutron/plugins/ml2/drivers/cisco/nexus/nexus_db_v2          99%
neutron/plugins/ml2/drivers/cisco/nexus/nexus_models_v2      65%
neutron/plugins/ml2/drivers/cisco/nexus/nexus_network_driver 98%
neutron/plugins/ml2/drivers/cisco/nexus/config               100%

NB: nexus_models_v2.py consists of database definitions and two
customization methods, __repr__ and __eq__.

Change-Id: I0de1cb9e71adffff698e37c8bec5497b88f0f0cd
Closes-Bug: 1267481
Merge "ML2 Cisco Nexus MD: Improve Unit Test Coverage"
Merge "gw_port should be set as lazy='join'"