openqa fixups from #77 review (double backticks, range)
    
    Fix up a couple of issues @bowlofeggs noted in #77 (the PR that
    added the openQA guide): double not single backticks, and use
    {1..10} to simplify the range in a command for restarting the
    workers.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>