unbound: make so-reuseport conditional upon RSS status

We only ask the tunables configuration layer for the current value
which is likely going to match.  We could fetch the actual value
from the system but speed and priviledge separation concerns weigh
heavier.

PR: https://forum.opnsense.org/index.php?topic=24409.0

src/etc/inc/plugins.inc.d/unbound.inc

@@ -295,6 +295,8 @@ EOD;
         }
     }
 
+    $so_reuseport = empty(system_sysctl_get()['net.inet.rss.enabled']) ? 'yes' : 'no';
+
     $unboundconf = <<<EOD
 ##########################
 # Unbound Configuration
@@ -322,7 +324,7 @@ do-ip6: {$do_ip6}
 do-udp: yes
 do-tcp: yes
 do-daemonize: yes
-so-reuseport: yes
+so-reuseport: ${so_reuseport}
 module-config: "{$module_config}"
 cache-max-ttl: {$cache_max_ttl}
 cache-min-ttl: {$cache_min_ttl}