docker/docker — pull request #8303 by coolljt0725 (2014-09-30 07:01:40+00:00)
Title: Fix the bug of set an existed tag name of a repository

When tag a image with a tag name which is existed in the repository,
docker should prompt it is conflicted and it will worked when with
a -f option.But the latest docker doesn't work like that,it will just
replace the image whether you have a -f option or not.View the
code you can find that if an repoName is existed,it will never go
to check if 'force' option is set or not.

Signed-off-by: Lei Jitang