Specify tenant_id when retrieving LBaaS/VPNaaS resource

In Neutron API, resources from all tenants are listed when
retrieving a list of resources with admin role. Horizon
project dashboard is for project-specific operations,
so we should retrieve only resources of the given project.
LBaaS/VPNaaS panels have this problem, but FWaaS does not.
router_list should be called with tenant_id filter too.

This commit also fixes VPN/FWaaS tests so that it extract tenant_id
from request attribute rather than use tenant_id of test_data.

Change-Id: I080e6c6d1e426a878c1d088763bbc7e5add15820
Closes-Bug: #1244126
(cherry picked from commit 630b43349160f8b35d54196aabaa6e1afe5e4d61)
Merge "Specify tenant_id when retrieving LBaaS/VPNaaS resource" into stable/havana