Pin jnr-unixsocket for Docker plugin to 0.13

Pin jnr-unixsocket for Docker plugin to 0.13

The current verison of jnr-unixsocket is 0.12 from the Docker
plugin however in order to be able the images for ARM64, it needs
the newer version which has support for it.

There is work upstream to switch the version to 0.18[0] however
it seems that this is still pending, so we can pin it for now until
that merges.

[0]: https://github.com/spotify/docker-maven-plugin/pull/379

Change-Id: Ieb1b5c6e43d3dc1425b2ab63f2fd161e452e5a57
Issue-ID: CIMAN-154
Signed-off-by: Mohammed Naser <mnaser@vexxhost.com>