Update resolvers.conf to break dns cache

By default, nginx caches answers using the TTL value of a response.
In a dynamic environment containers can get recreated with new IPs,
reducing the validity of the cache allows refreshing these IPs

https://nginx.org/en/docs/http/ngx_http_core_module.html#resolver

docker/rootfs/etc/services.d/nginx/run

@@ -24,7 +24,7 @@ chown root /tmp/nginx
 
 # Dynamically generate resolvers file, if resolver is IPv6, enclose in `[]`
 # thanks @tfmm
-echo resolver "$(awk 'BEGIN{ORS=" "} $1=="nameserver" { sub(/%.*$/,"",$2); print ($2 ~ ":")? "["$2"]": $2}' /etc/resolv.conf);" > /etc/nginx/conf.d/include/resolvers.conf
+echo resolver "$(awk 'BEGIN{ORS=" "} $1=="nameserver" { sub(/%.*$/,"",$2); print ($2 ~ ":")? "["$2"]": $2}' /etc/resolv.conf) valid=10s;" > /etc/nginx/conf.d/include/resolvers.conf
 
 # Generate dummy self-signed certificate.
 if [ ! -f /data/nginx/dummycert.pem ] || [ ! -f /data/nginx/dummykey.pem ]