Comment 29 for bug 1622616

Reviewed: https://review.openstack.org/374689
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=c201439a94d9249d1c3aefbf404304ffa1690be0
Submitter: Jenkins
Branch: stable/newton

commit c201439a94d9249d1c3aefbf404304ffa1690be0
Author: Carl Baldwin <email address hidden>
Date: Mon Sep 12 15:31:08 2016 -0600

    Try to reuse existing IPs when a port update specifies subnet

    If a port update specifies only a subnet_id for a fixed_ip then we
    want to look at existing fixed_ips to see if that subnet_id is already
    there. This avoids allocating a new IP address on the subnet and
    deallocating the old one.

    Without some special care, this breaks the code path for prefix
    delegation. One could argue that PD needs reworking. However, as a
    stop-gap measure, we still run the old code path if the address is an
    EUI-64 address. This allows PD to continue to work as it was
    originally written and it doesn't do any harm because allocating
    EUI-64 addresses is repeatable.

    This commit removes a test case from the DNS integration tests. The
    test was specifically testing that DNS records we updated in the case
    where a subnet id was passed to re-allocate a fixed_ip. Since the use
    case no longer works, the test doesn't make sense.

    This commit also preserves the ability to add an additional IP from a
    subnet for which the port already has IPs.

    Change-Id: Iba5d54efa7f99ed82275ffc8e5be975b373c29d3
    Related-Bug: #1622616
    Closes-Bug: #1625334
    (cherry picked from commit 14fee9cfcc816128606fc11d33800af90a0b1859)