Update bash-completion to reflect ability to push single tags

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)

contrib/completion/bash/docker

@@ -430,9 +430,7 @@ _docker_push()
 {
 	local counter=$(__docker_pos_first_nonflag)
 	if [ $cword -eq $counter ]; then
-		__docker_image_repos
-		# TODO replace this with __docker_image_repos_and_tags
-		# see https://github.com/dotcloud/docker/issues/3411
+		__docker_image_repos_and_tags
 	fi
 }