Fix DISABLE_IPV6 flag handling

The DISABLE_IPV6 flag did not turn off ipv6 DNS requests performed by
nginx. This commit changes it and makes nginx-proxy-manager more
compatible with podman.

Author: czocher

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

@@ -24,8 +24,12 @@ 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"]": $2}' /etc/resolv.conf) valid=10s;" > /etc/nginx/conf.d/include/resolvers.conf
-
+if [ "$DISABLE_IPV6" == "true" ] || [ "$DISABLE_IPV6" == "on" ] || [ "$DISABLE_IPV6" == "1" ] || [ "$DISABLE_IPV6" == "yes" ];
+then
+  echo resolver "$(awk 'BEGIN{ORS=" "} $1=="nameserver" { sub(/%.*$/,"",$2); print ($2 ~ ":")? "["$2"]": $2}' /etc/resolv.conf) ipv6=off valid=10s;" > /etc/nginx/conf.d/include/resolvers.conf
+else
+  echo resolver "$(awk 'BEGIN{ORS=" "} $1=="nameserver" { sub(/%.*$/,"",$2); print ($2 ~ ":")? "["$2"]": $2}' /etc/resolv.conf) valid=10s;" > /etc/nginx/conf.d/include/resolvers.conf
+fi
 # Generate dummy self-signed certificate.
 if [ ! -f /data/nginx/dummycert.pem ] || [ ! -f /data/nginx/dummykey.pem ]
 then