.gitignore: Ignore the correct rename example binary
    
    In e755186c5c305a9 we tried to introduce an example demonstrating
    new virDomainRename API. Unfortunately, in the .gitignore we had
    a different binary listed. It's 'rename' binary which we want git
    to ignore, not 'test'.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>