Fix acceptance tests

[danielparks]

Previously, acceptance tests were failing during the initial installation of fixtures:

Cloning into 'spec/fixtures/modules/puppet_agent'...
fatal: unable to connect to github.com:
github.com[0: 140.82.113.4]: errno=Connection timed out

This switches to using https URLs for the fixtures, which allows acceptance tests to proceed beyond that point.

---

I don’t normally use Docker, so it’s hard for me to tell what’s problem on my machine and what’s a problem with the acceptance testing setup. I’m getting errors while spinning up the CentOS container:

Failure connecting to localhost:52595:
{"target"=>"localhost:52595", "action"=>"command", "object"=>nil, "status"=>"failure", "value"=>{"_error"=>{"details"=>{}, "kind"=>"puppetlabs.tasks/connect-error", "msg"=>"Failed to connect to localhost:52595: pkeys are immutable on OpenSSL 3.0", "issue_code"=>"CONNECT_ERROR"}}}

[danielparks]

Looks like those errors are on my end, since they succeed in Travis. I also took the opportunity to add the new (?) location of the Litmus inventory file to .gitignore.

[chelnak]

This fix is spot on. Thank you.