Reformat vendor.conf, update docker/docker and dependencies

[thaJeztah]

This updates docker/docker and its dependencies to what's currently the tip of the 19.03 branch.

Also reformats vendor.conf for readability; inspired by the formatting used in the Notary repository 😅

[thaJeztah]

ping @mavenugo @selansen @euanh PTAL

I realise this is a big diff; these are the versions of the dependencies that the libnetwork code is running on when vendored in moby/moby, so it's good to use the same versions here

[andrewhsu]

SGTM, @mavenugo this would be helpful for syncing up the vendor of go code so backports can go in more smoothly

[thaJeztah]

It's mainly to make sure that we're testing against the same version of the dependencies as we'll be using the libnetwork code in (when vendoring it into moby/moby).

Note that none of the vendored files are used in "production" (as we strip the vendor directory when vendoring libnetwork into moby)

[selansen]

LGTM

[arkodg]

@euanh PTAL