fixed some memory leak

util.cpp

@@ -283,6 +283,7 @@ namespace net
 						inet_ntop(af, &((sockaddr_in6 *)cur->ifa_addr)->sin6_addr, addr, INET6_ADDRSTRLEN);
 					freeifaddrs(addrs);
 					std::string cur_ifaddr(addr);
+					delete[] addr;
 					return boost::asio::ip::address::from_string(cur_ifaddr);
 				}
 				cur = cur->ifa_next;