tests: specify the devices for OSDs in the scenario for collocation

Signed-off-by: Alfredo Deza <adeza@redhat.com>

Resolves: colocated#tests

tests/functional/centos/7/journal-collocation/scenario.py

@@ -14,6 +14,7 @@ nodes = {
     },
     'osd0': {
         'username': 'vagrant',
-        'components': [],
+        'components': ['collocated_journals'],
+        'devices': ['/dev/sda', '/dev/sdb'],
     },
 }