openqa/worker: set up swtpm service on tap worker hosts
    
    swtpm is a TPM emulator we want to use for testing Clevis on
    IoT (and potentially other things in future). We're implementing
    this by having os-autoinst just add the qemu args but expect
    swtpm itself to be running already - that's counted as the
    sysadmin's responsibility. My approach to this is to have openQA
    tap worker hosts also be tpm worker hosts, meaning they run one
    instance of swtpm per worker instance (as a systemd service) and
    are added to a 'tpm' worker class which tests can use to ensure
    they run on a suitably-equipped worker. This sets up all of that.
    We need a custom SELinux policy module to allow systemd to run
    swtpm - this is blocked by default.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>