Increase respawn limit for upstart-controlled container

After docker was successfully started by upstart, starting a container
will fail until the daemon has finished initializing, which can take a
while when many images/containers are present. By default, upstart will
retry 5 times separated by 10s. This patch override these defaults to
allow up to 2min for the daemon initialization (12 attempts, every 10s).

Docker-DCO-1.1-Signed-off-by: Brice Jaglin <bjaglin@teads.tv> (github: bjaglin)