Remove the Azure-local vm_extra_create_disk(), since we no longer
need qemu-img to convert the final VHD image to an Azure-compatible
format.

Although the waagent utility is installed from ports, create the
symlink to /usr/sbin, pending investigation on where this is
hard-coded, so it can be reported upstream.

Append the hour and minute to the snapshot suffix for EC2
AMIs and Azure VM images.  This is particularly helpful for
testing to avoid name collisions, but also useful for cases
where a necessary rebuild is done before the date changes.