Docker not uninstalled on installation failure

[embray]

If the Sage installer installs docker, but then later fails with an error, it leaves Docker installed. Obviously if docker was already installed we shouldn't touch it. But if Docker was never previously installed, and our installer fails, we shouldn't be leaving any trace behind, so we should make sure the Docker installation is rolled back too.

[dimpase]

looks like an unnecessary complex way to do things here. IMHO Sage installer should not install Docker...