do not output a user unfriendly line

do not output a user unfriendly line

"Switching host model to compound since you changed the network and/or cpu model(s)"

- Hard to understand what's going on without reading the right part of
  the source.
- I cannot think of a situation where this would do any good

- My evil plan is to change the xbt_lib of all hosts by a boost map of
  Hosts, so the host model will be gone, and hosts will always
  dispatch to their content. One this is done, objectifying everything
  will be really easy.