fix rare race condition that causes infinite loop

if we get a sigchld but all our children are gone by the time we get
around to reaping them (i don't think this should ever happen, but it
just did), then we'd loop forever trying to reap them.


svn:r2141

src/or/main.c

@@ -842,7 +842,7 @@ static int do_main_loop(void) {
       please_reset = 0;
     }
     if(please_reap_children) {
-      while(waitpid(-1,NULL,WNOHANG)) ; /* keep reaping until no more zombies */
+      while(waitpid(-1,NULL,WNOHANG) > 0) ; /* keep reaping until no more zombies */
       please_reap_children = 0;
     }
 #endif /* signal stuff */