mgr/telemetry: check get_metadata return val

get_metada() returns 'None' when requesting a missing service, hence
trying to access its content fails. Added a check for osd and mgr
get_metadata() calls.

Fixes: https://tracker.ceph.com/issues/43642
Signed-off-by: Yaarit Hatuka <yaarit@redhat.com>

src/pybind/mgr/telemetry/module.py

@@ -227,7 +227,11 @@ def gather_osd_metadata(self, osd_map):
             metadata[key] = defaultdict(int)
 
         for osd in osd_map['osds']:
-            for k, v in self.get_metadata('osd', str(osd['osd'])).items():
+            res = self.get_metadata('osd', str(osd['osd'])).items()
+            if res is None:
+                self.log.debug('Could not get metadata for osd.%s' % str(osd['osd']))
+                continue
+            for k, v in res:
                 if k not in keys:
                     continue
 
@@ -244,7 +248,11 @@ def gather_mon_metadata(self, mon_map):
             metadata[key] = defaultdict(int)
 
         for mon in mon_map['mons']:
-            for k, v in self.get_metadata('mon', mon['name']).items():
+            res = self.get_metadata('mon', mon['name']).items()
+            if res is None:
+                self.log.debug('Could not get metadata for mon.%s' % (mon['name']))
+                continue
+            for k, v in res:
                 if k not in keys:
                     continue