Wire up SIGUSR2 to kill blocking threads

Get rid of io engine ops SIGTERM flag, it didn't really
work.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/engines/net.c b/engines/net.c
index 8957545..81e173c 100644
--- a/engines/net.c
+++ b/engines/net.c
@@ -881,6 +881,11 @@
 	return 0;
 }
 
+static void fio_netio_terminate(struct thread_data *td)
+{
+	kill(td->pid, SIGUSR2);
+}
+
 #ifdef FIO_HAVE_SPLICE
 static int fio_netio_setup_splice(struct thread_data *td)
 {
@@ -909,11 +914,12 @@
 	.init			= fio_netio_init,
 	.cleanup		= fio_netio_cleanup,
 	.open_file		= fio_netio_open_file,
-	.close_file		= generic_close_file,
+	.close_file		= fio_netio_close_file,
+	.terminate		= fio_netio_terminate,
 	.options		= options,
 	.option_struct_size	= sizeof(struct netio_options),
 	.flags			= FIO_SYNCIO | FIO_DISKLESSIO | FIO_UNIDIR |
-				  FIO_SIGTERM | FIO_PIPEIO,
+				  FIO_PIPEIO,
 };
 #endif
 
@@ -927,10 +933,11 @@
 	.cleanup		= fio_netio_cleanup,
 	.open_file		= fio_netio_open_file,
 	.close_file		= fio_netio_close_file,
+	.terminate		= fio_netio_terminate,
 	.options		= options,
 	.option_struct_size	= sizeof(struct netio_options),
 	.flags			= FIO_SYNCIO | FIO_DISKLESSIO | FIO_UNIDIR |
-				  FIO_SIGTERM | FIO_PIPEIO,
+				  FIO_PIPEIO,
 };
 
 static int str_hostname_cb(void *data, const char *input)