for division not accurate division

[jianfeng zhang]

for workload_balance strategy

when choice host
code is like

(src_instance_workload + workload) < self.threshold / 100 * host.vcpus)

by default ‘/’ will be 0 so cannot get avaialbe host

so we should use accurate division

by ‘from __future__ import division’

[jianfeng zhang (zhangjianfeng)]

code commit at :https://review.openstack.org/#/c/463296/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/463296
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=2b152bf17c5c12b722d01c9711c57e78261be784
Submitter: Jenkins
Branch: master

commit 2b152bf17c5c12b722d01c9711c57e78261be784
Author: zhangjianfeng <[e-mail]>
Date: Mon May 8 18:23:40 2017 +0800

    [bugfix]for division use accurate division

    for now / just get int value ,this will lead method
    filter_destination_hosts return 0 host
    because self.threshold / 100 * host.vcpus is 0
    so we need use accurate division to change this

    close-bug: 1689269

    Change-Id: I5663951ce750d6c4580a507ccfc0268baea0685f