Proposal: Use docker client library

[jimmyxian]

Docker Master code have already extracted a standalone client library(moby/moby#18472) from the cli that can be used outside of docker. I think we should use that library instead of dockerclient.

/cc @docker/swarm-maintainers

[jimmyxian]

But it does not have mock module. It will have a impact on our tests.

[abronan]

I think this is the way to go, even though it might be quite tricky as of now.

For example in dockerclient, on top of the test mocking issue, we also have the nopclient which voids every actions once the Engine goes down. It avoids heavy locking around the engine list/struct and pending operations (it would usually panic rarely on refresh because of this). So I'm not sure we can migrate right away before we get the same constructs from the client library on the Engine side.

[MHBauer]

Good to have this issue to track. Give it some time to move to it's final location.

[nishanttotla]

Closing this issue since discussion is being tracked in #1879. Please review PR #1880 for a starter implementation of introducing the engine-api.

[jimmyxian]

@nishanttotla Great!