Create HA router shows successful when there is only one l3 agent is active.

[Xu Han Peng]

When there is only one active l3 agent (others are stopped), HA router can still be successfully created
 although it cannot be scheduled. There is error log showing scheduling failure:

HANotEnoughAvailableAgents: Not enough l3 agents available to ensure HA. Minimum required 2, available 1.

$ neutron router-create router-ha --ha=True --distributed=False
Created a new router:
+-----------------------+--------------------------------------+
| Field | Value |
+-----------------------+--------------------------------------+
| admin_state_up | True |
| distributed | False |
| external_gateway_info | |
| ha | True |
| id | 11f228a0-c10c-47e8-b636-ee93c302b266 |
| name | router-ha |
| routes | |
| status | ACTIVE |
| tenant_id | 9b06aec0cc8a42d1a233696bb69212c5 |
+-----------------------+--------------------------------------+

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/154374

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/154374
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=c27310638bff452f54086cf027c442ad2a62e65f
Submitter: Jenkins
Branch: master

commit c27310638bff452f54086cf027c442ad2a62e65f
Author: Xu Han Peng <email address hidden>
Date: Thu Apr 9 01:46:36 2015 -0400

    Not creating HA router when not enough l3 agents

    Currently a HA router can be successfully created even when
    there is not enough active l3 agent. Current code only checks
    existing l3 agents but does not check if the agent is already
    down.

    This patch fixes this problem by checking only active l3 agents
    when getting the number of agents for scheduling HA router.

    Closes-Bug: 1420117

    Change-Id: I6c1d108db1a7c93b61c0dd0b1ffee319a411b17a

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: neutron-pecan
Review: https://review.openstack.org/185072