This patch gets Ironic virt driver to support soft reboot.
Ironic API supports soft reboot since API version 1.27. The API
version has already been bumped to 1.28.
Change-Id: I4e61ebf852f61e3c0a511b49f0304d3138ef022e
Implements: blueprint soft-reboot-poweroff
Co-Authored-By: Tang Chen <chen.tang@easystack.cn>
Co-Authored-By: xiexs <xiexs@cn.fujitsu.com>