[SEBA-505] Do not check for existing ONU on subscriber delete

Change-Id: I4fa8cb00a327aefc37a5ef777d1f5dcff03e1056
diff --git a/xos/synchronizer/models/models.py b/xos/synchronizer/models/models.py
index 9713ab4..a9fbace 100644
--- a/xos/synchronizer/models/models.py
+++ b/xos/synchronizer/models/models.py
@@ -115,7 +115,7 @@
 
         self.set_owner()
 
-        if self.status != "pre-provisioned" and hasattr(self.owner.leaf_model, "access") and self.owner.leaf_model.access == "voltha":
+        if self.status != "pre-provisioned" and hasattr(self.owner.leaf_model, "access") and self.owner.leaf_model.access == "voltha" and not self.deleted:
 
             # if the access network is managed by voltha, validate that onu_device actually exist
             volt_service = self.owner.provider_services[0].leaf_model # we assume RCORDService is connected only to the vOLTService