docker.upstart: avoid spawning a `sh` process

start script / end script create an intermediate sh process.
docker.upstart: use the same start/stop events as sshd

Is probably more solid
Fixes 1136; Reopened from 1175 with latest changes.
Bind daemon to 0.0.0.0 in Vagrant. Fixes #1304
Do not show empty parenthesis if the default configuration is missing.
Remove unused argument.
Merge pull request #1322 from calavera/prompt_without_defaults

Do not show empty parenthesis if the default configuration is missing.
Merge pull request #1233 from fmd/1136-environment-variables

+ Builder: CmdAdd and CmdEnv now respect Dockerfile-set ENV variables
Merge pull request #1312 from titanous/vagrant-bind

Bind daemon to 0.0.0.0 in Vagrant
Merge pull request #1209 from zimbatm/upstart-improvements

Upstart improvements