setup-environment: Fix valid machine matching

We need to output the list one per line, otherwise the grep regexp
won't match.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>

Change-Id: I0c4f04f26a9b4af14739b959564f76dd330f5bd1
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>