metropolis/cli/metroctl: don't try to use the bundle as installer

This slipped in when I refactored the install command, woops.

Change-Id: I5c6178f9dcf4840b0d7efe9b6e62e35df242f7ae
Reviewed-on: https://review.monogon.dev/c/monogon/+/2927
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/cli/metroctl/cmd_install.go b/metropolis/cli/metroctl/cmd_install.go
index f729d34..fdc51b0 100644
--- a/metropolis/cli/metroctl/cmd_install.go
+++ b/metropolis/cli/metroctl/cmd_install.go
@@ -126,7 +126,7 @@
 		return bytes.NewReader(df)
 	}
 
-	f, err := blkio.NewFileReader(*bundlePath)
+	f, err := blkio.NewFileReader(*flag)
 	if err != nil {
 		log.Fatalf("Failed to open specified %s: %v", name, err)
 	}