Fix issues in OpenSSH Runroot method found by real tests.
    
    - Pass the runroot_tag to init command in OpenSSH Runroot method.
      This is needed for the init command as a source for initial packages
      for the buildroot.
    - Rename the "runroot_ssh_init_command" to "runroot_ssh_init_template"
      to make it consistent with the rest of "runroot_ssh_*" options.
    - Add missing "runroot_ssh_*" options to checks.py.
    - Use chmod/chown to `output_dir` in OpenSSH Runroot method the same way
      as it is used in Koji runroot method to make the runroot output readable
      for Pungi user.
    
    Signed-off-by: Jan Kaluza <jkaluza@redhat.com>