utils/broadcastwriter -> pkg/broadcastwriter

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
utils.Debugf -> log.Printf, move jsonlog to own package.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
port usage of jsonlog to the new daemon files which were refactored
recently.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #7329 from erikh/move_broadcastwriter

Cleanup: utils/broadcastwriter -> pkg/broadcastwriter