router: restart dhcpcd on ppp interface creation

hosts/router/ppp.nix

@@ -5,6 +5,7 @@
     path = "/etc/ppp/pap-secrets";
     mode = "0440";
   };
+
   # Setting default routes based on interfaces in different tables
   environment.etc."ppp/ip-up" = {
     text = ''
@@ -58,6 +59,8 @@
          ${pkgs.iproute2}/bin/ip -6 route replace default dev ppp-uplink-b metric 1000
          ;;
       esac
+
+      ${pkgs.systemd}/bin/systemctl restart dhcpcd.service
     '';
     mode = "555";
   };