OSU OSL : add diskimages to nb03

I forgot to add the diskimages here for nb03 to upload them.

Change-Id: Id5f053f0b2c0dac82fcb5cf254d4b162530e1c8b

nodepool/nb03.opendev.org.yaml

@@ -16,7 +16,7 @@ providers:
     region-name: 'RegionOne'
     cloud: linaro-us
     rate: 0.25
-    diskimages:
+    diskimages: &arm64_diskimages
       - name: ubuntu-xenial-arm64
         pause: false
         config-drive: true
@@ -74,6 +74,12 @@ providers:
           hw_disk_bus: scsi
           hw_scsi_model: virtio-scsi
 
+  - name: linaro-us
+    region-name: 'RegionOne'
+    cloud: linaro-us
+    rate: 0.25
+    diskimages: *arm64_diskimages
+
 diskimages:
   - name: base
     abstract: True