Start redis after network is online (#7639)

The two lines allow systemd to start redis.service after the network is online. Only after the network is online that Redis could bind to IP address other than 127.0.0.1 during initial boot up process.

utils/systemd-redis_server.service

@@ -20,6 +20,8 @@ Description=Redis data structure server
 Documentation=https://redis.io/documentation
 #Before=your_application.service another_example_application.service
 #AssertPathExists=/var/lib/redis
+Wants=network-online.target
+After=network-online.target
 
 [Service]
 ExecStart=/usr/local/bin/redis-server --supervised systemd --daemonize no