Fixed image_name from image-name in upload-to-image

This fix addresses an issue where the variable name for image_name
was incorrect, causing the image_name parameter to be sent as null
when using "cinder upload-to-image" from cli with v2 of the API

Change-Id: I62f8bbb4397526fb291a46777d9025318da8e5b3
Closes-Bug: 1274552
Merge "Fixed image_name from image-name in upload-to-image"