Add a script for generating CA signed certs, and a client cert.

@filbranden @jbeda Take a look.  @derekwaynecarr is there an easy way to get the IP address on a vagrant cluster?
I'd prefer that we use mktemp and delete the directory afterwards.  We do that in various places in our bash scripts:

```bash
local cert_temp=$(mktemp -d -t make-ca-cert.XXXXXX)
trap "rm -rf \"${cert_temp}\"" EXIT
cd "$cert_temp"
```