Upgrade Docker to 1.12.6.

[jgoclawski]

Fixes #1439 and #1518.

Based on #1542, but without forwarding issues, as those changes are introduced in Docker 1.13+.
We've tested #1542 to use overlay2 instead of overlay (#1380) and we're seeing great performance and stability improvements.

Can one of the admins trigger the ISO build, please? We'd love to test it internally, play around and give feedback.

[minikube-bot]

Can one of the admins verify this patch?

[codecov-io]

Codecov Report

Merging #1658 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1658   +/-   ##
=======================================
  Coverage   38.65%   38.65%           
=======================================
  Files          51       51           
  Lines        2667     2667           
=======================================
  Hits         1031     1031           
  Misses       1455     1455           
  Partials      181      181

---

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[dlorenc]

@minikube-bot ok to test

[jgoclawski]

Thanks for running the tests. It seems that all that should work have passed :)

If anyone wants to try the upgraded Docker 1.12, here is the command:
minikube start --iso-url https://storage.googleapis.com/minikube-builds/1658/minikube-testing.iso

I'm running this with storage driver changed from default overlay to overlay2:
minikube start --iso-url https://storage.googleapis.com/minikube-builds/1658/minikube-testing.iso --docker-opt storage-driver=overlay2

So far, so good, I haven't noticed any problems.

[dlorenc]

I think we should go ahead and take this. Thanks @jgoclawski!

[jgoclawski]

Thanks!