Create volume fail when image id is ""

When call create volume api with image id "", it will create an empty
volume.
But when create volume with snapshot id "" or srv volume "", it will
return an 404 error.
So it should create volume fail when call create volume api with image id
"".

Change-Id: If2c7b061753bbbd172a09d35b343e73e90a1b7b4
Closes-Bug: #1302609
Merge "Create volume fail when image id is """