Integration test to verify docker container builds

[chungers]

Added a new test which is essentially a container version of the tutorial test. The test runs by starting the plugins as Docker containers and made sure that discovery works, CLI works, and we can go through the tutorial as the test scenario.

This test has been incorporated as part of the docker build. To run the test by itself:

scripts/container-test

Signed-off-by: David Chung david.chung@docker.com

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "dockerfile-changes" git@github.com:chungers/infrakit.git somewhere
$ cd somewhere
$ git rebase -i HEAD~842353348088
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.