Set swssconfig.sh startsecs=0 for quick exit (#2181)

The default startsecs is 1 second. However, swssconfig.sh will quickly
exit with expected exit code 0 during warm starting. This case should
not be treated as a failure

dockers/docker-orchagent/supervisord.conf

@@ -57,6 +57,7 @@ priority=7
 autostart=false
 autorestart=unexpected
 startretries=0
+startsecs=0
 stdout_logfile=syslog
 stderr_logfile=syslog