Fix start/stop return active/stopped immediately in EC2 API

start/stop action is async. But the EC2 API is hard code the status
as start/stop finished immediately.

This patch fix start action return pending status, and stop action
return stopping status.

Change-Id: I0cf6db1dcb17c48a12fd62b0d707afd124b96b26
Closes-Bug: #1373230
Merge "Fix start/stop return active/stopped immediately in EC2 API"