conpaas: pass vm_id info to create_volume

On EC2, a storage volume has to be created in the same availability zone as the
VM one wants to attach it to. Change create_volume() accordingly.



git-svn-id: svn://svn.forge.objectweb.org/svnroot/contrail/trunk/conpaas@5237 ef35cc4a-2640-4bbf-98bc-65920db7d8ae