Docker permission strategy warning when Docker version can't be detected

[TimMoore]

The Docker plugin attempts to detect the current running Docker version, and validate that the selected permission strategy is compatible with the detected version.

If None is detected, it doesn't warn the user that they have an incompatible strategy (either by default or set manually).

I'm thinking that if None is detected it should print a different warning that the version couldn't be detected, but still try to proceed with the selected strategy rather than failing. At least then people won't think the problem is a bug in sbt-native-packager (or one of its downstream dependencies).

Originally posted by @TimMoore in #1230 (comment)

[muuki88]

At least then people won't think the problem is a bug in sbt-native-packager (or one of its downstream dependencies).

Hopefully 😂

I agree. We should hope for the best and only print a warning to the user.