m/n/b/mkimage/osimage: rename osimage.Create to osimage.Write

We aren't creating an osimage, we are writing it to a disk.

Change-Id: If3769e18dbe988556b0c607ad82b734f21637836
Reviewed-on: https://review.monogon.dev/c/monogon/+/3294
Reviewed-by: Leopold Schabel <leo@monogon.tech>
Tested-by: Jenkins CI
diff --git a/cloud/agent/install.go b/cloud/agent/install.go
index 6082337..66cd236 100644
--- a/cloud/agent/install.go
+++ b/cloud/agent/install.go
@@ -144,7 +144,7 @@
 		Output:         rootDev,
 	}
 
-	be, err := osimage.Create(&installParams)
+	be, err := osimage.Write(&installParams)
 	if err != nil {
 		return err
 	}