Fix mxs1980_blr_galera_server_ids

A housekeeping task cannot be removed by name from within the
task function itself. Instead the function must simply return
false.

maxutils/maxbase/src/worker.cc

@@ -1032,7 +1032,10 @@ bool Worker::cancel_delayed_call(uint32_t id)
     }
     else
     {
-        mxb_assert(!true);
+        mxb_assert_message(!true,
+                           "Attempt to remove delayed call using non-existent id %u. "
+                           "Calling hktask_remove() from the task function? Simply "
+                           "return false instead.", id);
         MXB_WARNING("Attempt to remove a delayed call, associated with non-existing id.");
     }
 

server/modules/routing/binlogrouter/blr_master.cc

@@ -1470,7 +1470,6 @@ static bool blr_check_last_master_event(void* inst)
                      "%s heartbeat",
                      router->service->name());
 
-            hktask_remove(task_name);
             router->heartbeat_task_active = false;
         }