Fix for failed download

Hello again!

If for any reason the CopperEgg install script fails to download, the recipe will actually **uninstall** the CopperEgg agent.


The `installed_ver` variable is empty and won't match the `collver` variable and thinks it's an update and will go though the uninstall process and try to run a failed download `chef.sh` script. 

This fix will check to ensure that `install_ver` actually contains data before doing anything.