Added a new API reload_all() for reloading all devices in a cluster at a time.
Modified reload_reboot_for_interface_attachment() and reload_reboot_for_interface_detachment() to use new API (to replace self.reload()) to reload_all VCS cluster devices.
Description
Added a new API reload_all() for supporting dynamic interface detection enhancement.
Related PR of a10-octavia side:
https://github.com/a10networks/a10-octavia/pull/480
Jira tickets
https://a10networks.atlassian.net/browse/STACK-2473 https://a10networks.atlassian.net/browse/STACK-2474
Technical Approach