Support docker "rootless" mode

[cylewitruk]

The relatively new rootless docker mode isn't supported and results in Clarinet failing to be able to start a devnet:

This is probably simply due to how Clarinet is using Bollard to look for the instance to connect to. In rootless mode the unix socket is in another path, for example for me it's unix:///var/run/user/1000/docker.sock instead of /var/run/docker.sock. So you probably need to check both the user path and the global path.