[VOL-3410] Fix naming of the GPON configurations

Change-Id: I1a57f04b4c879f0ae9a70d50e3482c20e8605a49
diff --git a/tests/data/onf-demo-pod-sadis-DT-GPON.json b/tests/data/onf-demo-pod-gpon-sadis-DT.json
similarity index 100%
rename from tests/data/onf-demo-pod-sadis-DT-GPON.json
rename to tests/data/onf-demo-pod-gpon-sadis-DT.json