Do not allow HEAD images/detail

Currently, a HEAD images/detail request goes through the images/{id}
route which leads to a 500 response status.
This HEAD method should be handled separetely in order to return a
405 Method Not Allowed response and suggest GET as an allowed method.

Change-Id: Ic83e819189bcff7c4735af476217a9ed1e4f41b8
Closes-Bug: #1297358
Merge "Do not allow HEAD images/detail"