software/kvm: install slapos.cookbook with its dedicated parts

some depends egg have special installation methods, we need more than
just listing the egg to install it.

software/kvm/software.cfg

@@ -50,7 +50,7 @@ eggs =
   ${python-cffi:egg}
   ${lxml-python:egg}
   websockify
-  slapos.cookbook
+  ${slapos-cookbook:eggs}
   erp5.util
 # BBB: eggs used as recipe should be kept otherwise sections depending
 # on it can't be uninstalled