Allow RP_MODE to be fed in from ADO

.pipelines/e2e-with-billing.yml

@@ -17,7 +17,7 @@ stages:
         subscription: $(e2e-subscription)
         azureDevOpsE2EJSONSPN: $(aro-v4-e2e-devops-spn)
         aroVersionStorageAccount: $(aro-version-storage-account)
-        rpMode: int
+        rpMode: $(RP_MODE)
 - stage: Delay_For_Billing_Table
   displayName: Wait 6 hours for billing table ready
   jobs: