Change default value of resize_confirm_window to -1

[Guangya Liu (Jay Lau)]

Now the default value of resize_confirm_window is 0, 0 means auto confirm was disabled.

For some cases, admin might want to confirm immediately, but the minimum value is 1 which means that we need to wait at least one second.

Also the auto confirm resize logic was in a periodic task, if the periodic task interval was 60s, and even if we set resize_confirm_window as 1 we might still need to wait 60s before auto confirm.

So we should set the default value of resize_confirm_window to -1 which means auto confirm was disabled and 0 means auto confirm immediately

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/65637

[Joe Gordon (jogo)]

this is a backwards incompatible change as is.