[ibm] create_image should do a PUT, not a POST, and needs 'state' param

lib/fog/ibm/requests/compute/create_image.rb

@@ -22,10 +22,11 @@ module Fog
         #     * 'state'<~Integer>: status of image
         def create_image(instance_id, name, description)
           request(
-            :method   => 'POST',
+            :method   => 'PUT',
             :expects  => 200,
             :path     => "/instances/#{instance_id}",
             :body     => {
+              'state'       => 'save',
               'name'        => name,
               'description' => description
             }