blktrace: load improvements

- Set the state explicitly to SETTING_UP when loading the
  traces. This could take a while, so tell the status thread
  that we are setting up so it knows how to display us
  correctly.

- Fix a bug with multiple devices where we didn't cache the
  major/minor properly. This made blktrace spend tons of CPU
  cycles looking up /sys.

- Handle multiple devices correctly when adding files.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/engines/net.c b/engines/net.c
index dd06861..1df8d06 100644
--- a/engines/net.c
+++ b/engines/net.c
@@ -1194,7 +1194,7 @@
 	struct netio_data *nd;
 
 	if (!td->files_index) {
-		add_file(td, td->o.filename ?: "net", 0);
+		add_file(td, td->o.filename ?: "net", 0, 0);
 		td->o.nr_files = td->o.nr_files ?: 1;
 	}