Missing verification of supported subnetpools neutron extensions

[Irena Berezovsky]

Kuryr requires neutron to support subnetpool extension in order to provide proper IPAM support.
Kuryr should query neutron for the supported extensions during its initialization and check if subnetpools extension is listed.
Otherwise kuryr should not proceed

[Pengfei Ni (feiskyer)]

subnetpools is a basic resource in neutron from kilo. I think kuryr should document that it's only working at kilo or upgrade versions.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/234579

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/234579
Committed: https://git.openstack.org/cgit/openstack/kuryr/commit/?id=7dfecfd1f312a519da9b8cebd6979f7be9fa93b3
Submitter: Jenkins
Branch: master

commit 7dfecfd1f312a519da9b8cebd6979f7be9fa93b3
Author: Vikas Choudhary <email address hidden>
Date: Wed Oct 14 11:12:04 2015 +0530

    Check subnetpool extension support

    This fix is to add support for checking subnetpool extension support
    at Kuryr server startup time. If required extension is found missing,
    startup script will exit and kuryr driver server will not start.

    Change-Id: I264be36c1b3b23517f4f2ff741f51a5a86b2ae9f
    Closes-Bug: #1498393