Found a few issues with the setup for the Jenkins chapter

I found a few issues, along with some solutions that I wanted to pass along when doing the initial setup of the infrastructure for the chapter on Jenkins.

(1) Vagrantfile - Newer versions of virtualbox won't work out of the box with the subnet being used for the private_network definition. I changed that from 192.168.76.76 to 192.168.56.76 and that fixed that issue. ( https://www.virtualbox.org/manual/ch06.html#network_hostonly)

(2) apt cache is expired on the ubuntu2004 vagrant box, so I added a pre task in the provision.yml to refresh the apt cache. I was getting "url not found" errors when it was trying to install packages.

(3) when installing Jenkins via the geerlingguy.jenkins role, I was getting an error that stated: _Failed to update apt cache: E:The repository ''https://pkg.jenkins.io/debian binary/ Release'' does not have a Release file.'_ I was able to narrow this down to an old version of the ca-certificates package on ubuntu 2004, that needed to be updated before jenkins could be installed. I added a task to the geerlingguy.jenkins/tasks/setup_Debian.yml file to make sure that ca_certificates was set to latest which fixed the problem.

Once I fixed the three issues I found, I was able to get a vagrant up to succeed without an error on the first try.

Start by reviewing the Jenkins chapter's Vagrantfile and provision.yml, then inspect geerlingguy.jenkins/tasks/setup_Debian.yml. Run `vagrant up` with the chapter setup to reproduce the installation path. Done means the private network, apt package installation, and Jenkins provisioning complete without errors.

Written by the indexing model from the issue text.