openingd: ensure that revents fields are initialized.

Valgrind error file: valgrind-errors.112365
==112365== Conditional jump or move depends on uninitialised value(s)
==112365==    at 0x1105E0: main (openingd.c:1504)
==112365== 
==112365== Conditional jump or move depends on uninitialised value(s)
==112365==    at 0x110604: main (openingd.c:1507)
==112365== 
==112365== Conditional jump or move depends on uninitialised value(s)
==112365==    at 0x110628: main (openingd.c:1510)
==112365==

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

openingd/openingd.c

@@ -1497,6 +1497,12 @@ int main(int argc, char *argv[])
 			t = time_to_msec(trel);
 		else
 			t = -1;
+
+		/*~ If we get a signal which aborts the poll() call, valgrind
+		 * complains about revents being uninitialized.  I'm not sure
+		 * that's correct, but it's easy to be sure. */
+		pollfd[0].revents = pollfd[1].revents = pollfd[2].revents = 0;
+
 		poll(pollfd, ARRAY_SIZE(pollfd), t);
 		/* Subtle: handle_master_in can do its own poll loop, so
 		 * don't try to service more than one fd per loop. */