MINOR: epoll: always initialize all of epoll_event to please valgrind

valgrind complains that epoll_ctl() uses an epoll_event in which we
have only set the part we use from the data field (i.e. the fd). Tests
show that pre-initializing the struct in the stack doesn't have a
measurable impact so let's do it.

src/ev_epoll.c

@@ -61,7 +61,7 @@ static void __fd_clo(int fd)
 static void _update_fd(int fd)
 {
 	int en, opcode;
-	struct epoll_event ev;
+	struct epoll_event ev = { };
 
 	en = fdtab[fd].state;
 
@@ -120,7 +120,6 @@ static void _update_fd(int fd)
 	}
 
 	/* construct the epoll events based on new state */
-	ev.events = 0;
 	if (en & FD_EV_ACTIVE_R)
 		ev.events |= EPOLLIN | EPOLLRDHUP;