When ``changes-before`` < ``changes-since``, getting instance migrations records is null

[Brin Zhang]

This need to process the period time.
If ``changes-since`` and ``changes-before`` are all requested in rest URL, judge them:

The value of ``changes-since`` must be less than or equal to ``changes-before``, Otherwise return 400 error.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/607798

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/613070

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matt Riedemann (<email address hidden>) on branch: master
Review: https://review.openstack.org/613070

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/607798
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=a3a0068929136d3bf6e25338889fd3090938eac6
Submitter: Zuul
Branch: master

commit a3a0068929136d3bf6e25338889fd3090938eac6
Author: zhangbailin <email address hidden>
Date: Wed Oct 3 23:03:58 2018 -0400

    Add restrictions on updated_at when getting migrations

    If ``changes-before`` is less than ``changes-since`` in requested,
    there will get empty data when querying in db, so add the limit of
    these parameters. If ``changes-before`` < ``changes-since``, will
    be returned 400.

    Closes-Bug: #1796008
    Change-Id: I2a39ac5a9fe969d383099b4e766c46ad05d9f67c

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 19.0.0.0rc1 release candidate.