Allow configuration of max_overflow and max_pool_size in neutron.conf

[Mark DeVerter]

When we try beyond 50 concurrent VMs, we are getting some amount of failures due to below error in /var/log/neutron/neutron-metadata-agent.log

/var/log/neutron/neutron-metadata-agent.log:2015-06-02 11:41:04.342 775 ERROR neutron.agent.metadata.agent [-] Unexpected error.
/var/log/neutron/neutron-metadata-agent.log:2015-06-02 11:41:04.342 775 TRACE neutron.agent.metadata.agent ConnectionFailed: Connection to neutron failed: HTTPConnectionPool(host='172.22.192.250', port=9696): Max retries exceeded with url: /v2.0/ports.json?fixed_ips=ip_address%3D172.22.69.139 (Caused by <class 'socket.error'>: [Errno 111] ECONNREFUSED)

It seems, the below are the default Values getting substituted as these fields were not defined in neutron.conf
max_overflow: 10
max_pool_size: 5
pool_timeout: 30

We need an ability to configure these values in neutron.conf

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: juno
Review: https://review.openstack.org/187701

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/187701
Committed: https://git.openstack.org/cgit/stackforge/os-ansible-deployment/commit/?id=2b5c5c965035311708f7ef14d249527c27af6a2c
Submitter: Jenkins
Branch: juno

commit 2b5c5c965035311708f7ef14d249527c27af6a2c
Author: Mark DeVerter <email address hidden>
Date: Tue Jun 2 17:55:41 2015 +0000

    Add neutron SQL tuning

    Add variables for the following 3 neutron.conf vars:
    - max_overflow (default 10)
    - max_pool_size (default 5)
    - pool_timeout (default 30)

    This allows for sql tuning to better support bulk operations
    (boot/delete) with the ability to define custom values in
    neutron.conf based on business needs

    Moved variables back to:
    rpc_deployment/playbooks/vars/openstack_service_vars/neutron_server.yml

    Change-Id: I9770b9720a18be224d27677d2fe07e5d8d38a360
    Closes-Bug: #1461184