[IPAM] 'Internal' ipam driver does not allow to delete all pools on subnet update

[Pavel Bondar]

During investigation UT test failure 'test_port_update_deferred_allocation_no_ips' in [1] I found that attempt to update subnet providing blank ([]) allocation pools leads to silent ignoring this action on ipam driver side.

Reference ipam driver skips processing of the update request because of condition
"if not subnet_request.allocation_pools" in [2], which is too strict and
does not allow to clean up allocation pools on subnet update.

It is a because cleaning up allocation pools is a valid user action and built-in ipam implementation allows to do it.

Expected behavior:
Reference ipam driver should work the same as a built-in implementation and should allow to remove 'allocation_pools' on subnet update.

[1] http://logs.openstack.org/23/181023/89/check/gate-neutron-python27/2071f1d/testr_results.html.gz
[2] https://github.com/openstack/neutron/blob/38a080aca37197ff9c5464a3bc9981e684decee6/neutron/ipam/drivers/neutrondb_ipam/driver.py#L294

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/345498

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/345498
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=de2a70165c351abcc1266b79bae46fcd8ce68e59
Submitter: Jenkins
Branch: master

commit de2a70165c351abcc1266b79bae46fcd8ce68e59
Author: Pavel Bondar <email address hidden>
Date: Thu Jul 21 17:51:54 2016 +0300

    Fix updating allocation_pools on subnet update

    Reference IPAM driver skipped subnet_update processing
    if allocation_pools in subnet request are blank.

    Built-in ipam implementation allows to update allocation pools
    to blank value (i.e. clean up allocation pools for subnet).
    To make Reference ipam driver consistent with built-in ipam
    implementation allocation_pool check was removed.

    Included UT to verify that allocation pools can be updated to blank
    value now.

    Change-Id: I0654e46d4bc60f6cf51ffddeead238dd4f064db2
    Closes-Bug: #1605277

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 9.0.0.0b3 development milestone.