Fix 'os-start/os-stop' server actions for V2.1 API

'os-start/os-stop' server actions were missed for V2.1 API.
This patch converts 'os-start/os-stop' server action for V2.1 API

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

Closes-Bug: #1367575

Change-Id: I8b0f27fb639034d368bcc1fc51d20daf9c2cdeb5
Merge "Fix 'os-start/os-stop' server actions for V2.1 API"