Fix "revertResize/confirmResize" for V2.1 API

"revertResize/confirmResize" server actions were missed for V2.1 API.

This patch converts "revertResize/confirmResize" server action
for V2.1 API

The differences between v2 and v3 are described on the wiki page
https://wiki.openstack.org/wiki/NovaAPIv2tov3.

Change-Id: I24bdb5b28fafeb60ea7b4ff044b12a519498e592
Closes-Bug: #1367642
Merge "Fix "revertResize/confirmResize" for V2.1 API"