Removed hardcoded paths to private key

Without this patch, the hardcoded path of the private key prevents
to perform non-root executions of Oz.

The proposed patch gets this information from oz.cfg adding a new
parameter 'sshprivkey' that defaults to '/etc/oz/id_rsa-icicle-gen'
Use --yes on add-apt-repository so it is possible to use PPAs
add mageia