Make detection of image names more robust
Make detection of image names more robust

New version ( about Docker version 1.10.0-rc2) uses
sha256: as prefix of images. Old version of code had
problems, that was detecting second part after ':' as
tag.

pthierry38/openscap-daemon,baude/openscap-daemon,OpenSCAP/openscap-daemon,baude/openscap-daemon,pthierry38/openscap-daemon,OpenSCAP/openscap-daemon