docker::run and docker::exec lack refreshonly capability

[serverbiz]

Regular puppet exec has a refreshonly property which is very useful for using notify/subscribe to trigger the execution of commands that do not need to be executed on every puppet run. The best example is of such an event is a database upgrade. If we move the application into containers, we need a way to execute these same commands inside a container. The module currently doesn't seem to support that in an easy way.

Problem 1: docker::exec does not have a set-able refreshonly parameter

Adding a refreshonly parameter to docker:exec and the exec inside this define would be a useful addition.

Problem 2: docker::run does not support running a short-term foreground container

Unfortunately docker::exec would not over all use cases. It requires a container to already be running. In the case of my database migration example you would want to run this command before starting the service containers. So we need a way for docker::run to start a container, run the command and then automatically remove the container upon termination.

Doing this would require a few things:

1. Adding a Boolean parameter like refreshonly = false to docker::run.
2. Setting refreshonly=true would need to overrule $docker_run_flags array values resulting in --detach=false --rm=true. Note that the docker_run_flags parser does not yet support --rm.
3. Extending the existing exec "run ${title} with docker" with a refreshonly => $refreshonly parameter. Using the existing exec is perfect to support this since, like the restart policy code, a one-time command execution container does not need an init script.

This would be a great enhancement. Only requires adding a parameter, extending the docker_run_flags parser and (changing) some if-statements.