diskless replication rdb transfer uses pipe, and writes to sockets form the parent process.

misc:
- handle SSL_has_pending by iterating though these in beforeSleep, and setting timeout of 0 to aeProcessEvents
- fix issue with epoll signaling EPOLLHUP and EPOLLERR only to the write handlers. (needed to detect the rdb pipe was closed)
- add key-load-delay config for testing
- trim connShutdown which is no longer needed
- rioFdsetWrite -> rioFdWrite - simplified since there's no longer need to write to multiple FDs
- don't detect rdb child exited (don't call wait3) until we detect the pipe is closed
- Cleanup bad optimization from rio.c, add another one

src/aof.c

@@ -836,6 +836,8 @@ int loadAppendOnlyFile(char *filename) {
         freeFakeClientArgv(fakeClient);
         fakeClient->cmd = NULL;
         if (server.aof_load_truncated) valid_up_to = ftello(fp);
+        if (server.key_load_delay)
+            usleep(server.key_load_delay);
     }
 
     /* This point can only be reached when EOF is reached without errors.