Why do we want to control the version of Docker to install?

[gbraad]

In our codebase of the b2d ISO generation, we allow the Docker binary to be overwritten by another version:

https://github.com/gbraad/minishift-b2d-iso/blob/19496f2b01e56bc936bada0bdbe51e3ece674a88/iso/Dockerfile#L38-L47

This seems to be similar to: https://github.com/boot2docker/boot2docker/blob/master/Dockerfile#L305-L314

However, is this something we really want/need? To me this seems to be an unnecessary risk in quality, as we are unable to test. Especially due to the known breakage when Docker releases something new, and it depends on a kernel feature, etc, I do not think this is something we should really do.

WDYT? /cc: @praveenkumar @LalatenduMohanty @budhrg