This adds the changes-before filter to the servers,
os-instance-actions and os-migrations list for
filtering resources which were last updated before
or equal to the given time. The changes-before filter,
like the changes-since filter, will return deleted
server resources.
Depends-On: https://review.openstack.org/599276/
Part of bp support-to-query-nova-resources-filter-by-changes-before
Change-Id: I7c6ea00303374d605bda8ef1b62c5de1b4567696
4464a88737