[perf] Reduce job metrics reporting sleep interval to 15 seconds and disable MQTT debug logging

Author: charlieyl

python/fedml/core/mlops/mlops_job_perfs.py

@@ -175,7 +175,7 @@ def report_job_stats_entry(self, sys_event):
                     logging.debug("exception when reporting job pref: {}.".format(traceback.format_exc()))
                     pass
 
-            time.sleep(10)
+            time.sleep(15)
 
         logging.info("Job metrics process is about to exit.")
         mqtt_mgr.loop_stop()