[COOK-3453] - ssh_known_hosts cookbook ruby block executes on every chef run

Signed-off-by: Sean OMeara <someara@opscode.com>
Version bump to 1.2.0
Publish 1.2.0 Changelog
Version bump to 1.2.1 (for development)
Lazily load the host attribute for the current node when run on chef solo since the FQDN may have changed since Chef started and Ohai reloaded, thus without reading it lazily, we'd have the original value, not the reloaded value