CIFS support for secondary storage is documented here: https://cwiki.apache.org/confluence/display/CLOUDSTACK/CIFS+Support
It was implemented by extending the NFS provider. Its validation was updated so that you can pass it a URL containing the
details of a CIFS share.  The code that mounts NFS shares was extended to allow it do the same for CIFS shares.  Otherwise,
the secondary storage code is left unchanged.