Downgrade docker-cli to v1.18

[tdmanv]

Change Overview

Use alpine3.10 instead of 3.12 to select an earlier version of the docker cli. This will unblock an issue where older versions of the docker daemon could not release Kanister.

Build log: https://gist.github.com/ad4c7e3e1b0838f010ce4965bca84783

Pull request type

Please check the type of change your PR introduces:

• 🚧 Work in Progress
• 🌈 Refactoring (no functional changes, no api changes)
• 🐹 Trivial/Minor
• 🐛 Bugfix
• 🌻 Feature
• 🗺️ Documentation
• 🤖 Test

Test Plan

docker run --rm -it kan
isterio/build:v0.0.11 sh
/ # docker version
Client:
 Version:           18.09.8-ce
 API version:       1.39
 Go version:        go1.12.6
 Git commit:        0dd43dd87fd530113bf44c9bba9ad8b20ce4637f
 Built:             Sat Jul 20 15:20:06 2019
 OS/Arch:           linux/amd64
 Experimental:      false

• 💪 Manual
• ⚡ Unit test
• 💚 E2E

[viveksinghggits]

Hey @tdmanv
so the logs said

Error response from daemon: client version 1.40 is too new. Maximum supported API version is 1.37
: exit status 1

but even after this change, looking the the output that you have provided it seems the API version is still 1.39 (>1.37), not sure if thats gonna work.