[CLEANUP] accept: replace some inappropriate Alert() calls with send_log()

Some Alert() messages were remaining in the accept() path, which they
would have no chance to be detected. Remove some of them (the impossible
ones) and replace the relevant ones with send_log() so that the admin
has a chance to catch them.
diff --git a/src/frontend.c b/src/frontend.c
index f51a3d9..cbf6174 100644
--- a/src/frontend.c
+++ b/src/frontend.c
@@ -87,10 +87,9 @@
 	s->srv_error = default_srv_error;
 
 	/* Adjust some socket options */
-	if ((s->listener->addr.ss_family != AF_UNIX) && unlikely(setsockopt(cfd, IPPROTO_TCP, TCP_NODELAY, (char *) &one, sizeof(one)) == -1)) {
-		Alert("accept(): cannot set the socket in non blocking mode. Giving up\n");
+	if ((s->listener->addr.ss_family != AF_UNIX) &&
+	    setsockopt(cfd, IPPROTO_TCP, TCP_NODELAY, (char *) &one, sizeof(one)) == -1)
 		goto out_delete_cfd;
-	}
 
 	if (s->fe->options & PR_O_TCP_CLI_KA)
 		setsockopt(cfd, SOL_SOCKET, SO_KEEPALIVE, (char *) &one, sizeof(one));