load-tester can dynamically install a dedicated external IP for each IKE_SA

For consistency, the local/remote parameters have been replaced by the
initiator/responder options. As initiator, the initiator option can
be overriden by an addrs section taking key/value pairs with address
pools to use on a specific interface.

src/libcharon/plugins/load_tester/load_tester_config.h

@@ -35,6 +35,13 @@ struct load_tester_config_t {
 	 */
 	backend_t backend;
 
+	/**
+	 * Delete external IP if it was dynamically installed.
+	 *
+	 * @param ip			external IP
+	 */
+	void (*delete_ip)(load_tester_config_t *this, host_t *ip);
+
 	/**
 	 * Destroy the backend.
 	 */