Set somaxconn kernel parameter for Redis

See https://blog.codeship.com/adjusting-linux-kernel-parameters-with-docker-compose/

docker-compose.yml

@@ -1,4 +1,4 @@
-version: '2'
+version: '3'
 
 services:
   app:
@@ -37,6 +37,8 @@ services:
     restart: always
     volumes:
       - /data/redis:/data
+    sysctls:
+      net.core.somaxconn: 1024
   nginx:
     image: umputun/nginx-le:latest
     container_name: nginx