Prevent setting primary resolver if using custom DNS port (#861)

Most host managers doesn't support using custom DNS ports.
We are now disabling setting it up to avoid unwanted results

client/internal/dns/resolvconf_linux.go

@@ -5,8 +5,9 @@ import (
 	"os/exec"
 	"strings"
 
-	"github.com/netbirdio/netbird/iface"
 	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/iface"
 )
 
 const resolvconfCommand = "resolvconf"
@@ -21,6 +22,10 @@ func newResolvConfConfigurator(wgInterface *iface.WGIface) (hostManager, error)
 	}, nil
 }
 
+func (r *resolvconf) supportCustomPort() bool {
+	return false
+}
+
 func (r *resolvconf) applyDNSConfig(config hostDNSConfig) error {
 	var err error
 	if !config.routeAll {