Fix encryption key deletion error handling on volume delete

e.msg is only present for CinderExceptions, not all exception
types.

Closes-Bug: #1681874

Change-Id: I02601ae2a9ba95ab7145b86e24a094272f4cfbf6

cinder/volume/api.py

@@ -467,9 +467,12 @@ class API(base.Base):
         if encryption_key_id is not None:
             try:
                 self.key_manager.delete(context, encryption_key_id)
-            except Exception as e:
+            except exception.CinderException as e:
                 LOG.warning("Unable to delete encryption key for "
                             "volume: %s.", e.msg, resource=volume)
+            except Exception:
+                LOG.exception("Unable to delete encryption key for "
+                              "volume.")
 
         self.volume_rpcapi.delete_volume(context,
                                          volume,