Fix devices check for raw_multi_journal

Fix the logic for the mandatory devices check so that it applies to
raw_multi_journal and journal_collocation scenarios separately.

This fails otherwise because whichever var is "first" in the or is most
likely undefined.

roles/ceph-common/tasks/checks/check_mandatory_vars.yml

@@ -50,7 +50,7 @@
   fail: msg="please provide devices to your osd scenario"
   when:
     osd_group_name is defined and
-    (journal_collocation or raw_multi_journal) and
+    journal_collocation and
     devices is not defined
 
 - name: verify journal devices have been provided
@@ -58,7 +58,8 @@
   when:
     osd_group_name is defined and
     raw_multi_journal and
-    raw_journal_devices is not defined
+    (raw_journal_devices is not defined or
+    devices is not defined)
 
 - name: verify directories have been provided
   fail: msg="please provide directories to your osd scenario"