Docker manifest fetcher fails to handle HTTP redirects

Internal curl() function in Docker fetcher uses curl utility with -L (follow Location) and -i (include headers) flags to fetch manifests and then parses its output (a series of raw HTTP responses). curl silently drops the body of a “redirect” response from it's output while potentially non-zero Content-Length header field is still present. This makes ResponseDecoder consume headers of a next response and fail parsing or yield incorrect results.

Right now this is not a real issue because currently Docker Registry serves image manifests without redirects.