Switch to more consistently setting sockets non-blocking.

send.c

@@ -4,7 +4,6 @@
 #include <strings.h>
 #include <stdio.h>
 #include <unistd.h>
-#include <fcntl.h>
 #include <signal.h>
 
 #include "common.h"
@@ -98,11 +97,6 @@ struct serializer *send_get_serializer(char *name) {
 }
 
 void send_add(int fd, struct serializer *serializer) {
-	int flags = fcntl(fd, F_GETFL, 0);
-	assert(flags >= 0);
-	flags |= O_NONBLOCK;
-	assert(fcntl(fd, F_SETFL, flags) == 0);
-
 	if (!send_hello(fd, serializer)) {
 		fprintf(stderr, "S xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx: Failed to write hello\n");
 		return;