vl: Clean up after previous commit

Since the previous commit, find_machine() and find_default_machine()
don't have to deallocate on return.  This permits further
simplifications.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190405064121.23662-4-richardw.yang@linux.intel.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>