Additional network router RBAC tests

Add additional RBAC tests for network routers API, providing coverage
for the following policy actions:
    * create_router:ha
    * create_router:distributed
    * get_router:distributed
    * update_router:ha
    * update_router:distributed

Includes extension checks for l3-ha (high availability router tests) [0],
dvr (distributed router tests) [1], and ext-gw-mode (enable snat router
tests) [2].

[0] See description for ha attribute in link below.
[1] See description for distributed attribute in link below.
[2] See description for enable_snat attribute in link below.

https://developer.openstack.org/api-ref/networking/v2/?expanded=create-router-detail#create-router

Change-Id: I236d643f6320b8cc6c595bfcf52b5f5b5cd73378
2 files changed