Always install rsync from yum on RPM-based Linuxes

This commit runs `sudo yum install -y rsync` after the Chef Omnibus install on RPM-based Linuxes.

The core use case is for CentOS minimal, which does not include rsync.

See this issue: [Scientific Linux 6 minimal does not include rsync](https://github.com/matschaffer/knife-solo/pull/131) (https://github.com/matschaffer/knife-solo/pull/131)