virsh: Treat \n like ; in batch mode
    
    I wanted to do a demonstration with virsh batch mode, which
    takes multiple commands all packed into a single argument:
    
    $ virsh -c test:///default 'echo a; echo b;'
    a
    b
    
    but that produced a really long line, so I tried to make it
    more legible:
    
    $ virsh -c test:///default '
       echo a;
       echo b;
    '
    error: unknown command: '
    '
    
    Let's be more like the shell, and treat unquoted newline as a
    command separator just as we do for semicolon.  In fact, with
    that, I can even now mix styles:
    
    $ virsh -c test:///default '
       echo a; echo b
       echo c
    '
    a
    b
    c
    
    Signed-off-by: Eric Blake <eblake@redhat.com>
    Reviewed-by: John Ferlan <jferlan@redhat.com>