Prior to this commit, the docker action was using the method `prefix` on
an IPv4 and IPv6 address. This works fine for ruby versions 2.5 and
newer, however the ruby shipped with Vagrant is before 2.5, and
therefore the IPv4 and IPv6 classes do not have the prefix method,
resulting in an error. This commit fixes that by using a different
method of determining the prefix.
Use `mask` option for defining subnet on network configuration. Allow
options to be passed through using hash scoping and docker_network and
docker_connect prefixes. Enable public networks. Allow configuration
to define pre-existing networks by name.
Dan Čermák
Brian Cain
Chris Roberts