Run rsync with --rsync-path="rsync sudo" flag

[patcon]

knife-solo might be used first as the root user, and then as a another user after the first run creates it and locks down root login.

Can use --rsync-path to allow rsync to delete the files in the cache path as needed.

See: http://crashingdaily.wordpress.com/2007/06/29/rsync-and-sudo-over-ssh/

[tmatilai]

Closing this as there is a duplicate PR #125.