Improve the error msg of v2 image_data.py

Based on current implement, the error message of some upload
failures is missing the image id. It looks like: 'Unable to
upload duplicate image data for image: %s'.

Fixes bug 1207616

Change-Id: I608fb1ba84dde0e44a73e5e1bd3e850db49d84c4
Merge "Improve the error msg of v2 image_data.py"