Add postflight check of swarm nodes

[TylerJewell]

Signed-off-by: Tyler Jewell tjewell@codenvy.com

What does this PR do?

This PR adapts changes made to Eclipse Che to allow the inherited CLI to inherit its usage() statement from the core CLI so that as the base CLI makes improvements, the new CLI will have it inherited automatically.

Also provides a first implementation of a postflight check, which pulls the list of Swarm nodes from codenvy.env and then uses curl to ping each one's /info URL to see if it is reachable.

Must merge this at the same time as we merge: eclipse-che/che#3940

Changelog

Adapt CLI to changes in Eclipse Che #3940 and add postflight check of Swarm nodes as a test

Release Notes

We are working to make sure Codenvy starts in any environment perfectly every time. We've added some additional preflight checks related to mandatory minimums for disk and memory available from the host. If the minimums are not enough to start at least one workspace, then Codenvy bootup will be interrupted. Preflight checks can now be skipped with either --fast or --skip:preflight on the command line.

We have also introduced postflight checks. We parse codenvy.env to get a list of Swarm nodes for your cluster. We then check that each is reachable using curl and that their /info URL is returning valid data. A failure of this command is an early indicator that firewalls were not configured correctly. You can skip this check with --fast or --skip:postflight.

Docs PR

codenvy/docs#59

[TylerJewell]

@benoitf - as part of the testing, I would ask for you to adapt ARTIK and Codenvy SAAS to do the same. Note that there was a small refactoring of the method names and how I make use of pre_init and post_init in Che.

[benoitf]

I've updated methods name