util: fix tracevol.py to manage config map created by Rook

If the config map is created by rook then there won't be any provision to
specify subvolumeGroup, tracevol.py should skip looking for subvolumeGroup
in such case.

Signed-off-by: Mudit Agarwal <muagarwa@redhat.com>

troubleshooting/tools/tracevol.py

@@ -465,16 +465,19 @@ def get_subvol_group(arg):
     except ValueError as err:
         print(err, stdout)
         sys.exit()
-    cm_data = config_map['data']['config.json']
     subvol_group = ""
-    if "subvolumeGroup" in cm_data:
-        try:
-            cm_data_json = json.loads(cm_data)
-        except ValueError as err:
-            print(err, stdout)
-            sys.exit()
-        for data in cm_data_json:
-            subvol_group = data['cephFS']['subvolumeGroup']
+    cm_data = config_map['data'].get('config.json')
+    # Absence of 'config.json' means that the configmap
+    # is created by Rook and there won't be any provision to
+    # specify subvolumeGroup
+    if cm_data:
+        if "subvolumeGroup" in cm_data:
+            try:
+                cm_data_list = json.loads(cm_data)
+            except ValueError as err:
+                print(err, stdout)
+                sys.exit()
+            subvol_group = cm_data_list[0]['cephFS']['subvolumeGroup']
     return subvol_group
 
 def is_rbd_pv(arg, pvname, pvdata):