Add skeleton for pipeline client to run kvm-xfstests

[gctucker]

The first step is to get a local service that will be used as a basis for running kvm-xfstests on the dedicated builder. This won't be running in Docker but natively to simplify things and avoid issues with running KVM inside a container.

• [x] Add a fstests sub-directory in kernelci-pipeline to keep the files for this fstests PoC.
• [x] Add a fstests/runner.py script to run a service which will be listening for new tarball events
• [x] Just print a message to check the service is working when a new node is received

[gctucker]

As per the description, this can't be run in Docker so the service shouldn't be added to docker-compose. It will be run natively on the host. We may add a systemd configuration for it later, but this is only for the PoC anyway (a production solution would use something like GCE to start VMs rather than KVM locally).

[alexandrasp]

I see, it is better and made things a bit easier as well! I will update the PR accordingly.