Install (rightfully) fails when Docker is installed, but this is hard to troubleshoot

[NicolasT]

When docker is installed on a host, the installation fails (and should fail). docker has a Provides for runc which we want to install, but it's not a 'good' version of runc (and containerd). At some later point in time, install will then fail for obscure reasons.

#2960 could help to make the late error a bit more clear, but it's still difficult to link this (as a user) to docker being installed on the system.

As such, it likely makes sense to keep some kind of blacklist of 'known incompatible' packages, and ensuring these are not installed, either in a Salt state (somehow?), or in bootstrap.sh (though then the same checks would not be performed on non-bootstrap nodes...)

Known conflicting packages:

• docker
• containerd.io
• Alternative Salt versions?
• Also see What to do when the 'Inject nginx image' step fails? #2989 (reply in thread)

Also suggested by @Baitanik in #2989 (comment) and reported earlier by @vrancurel.