introduce check_onu_exist_on_discovery flag for openolt adapter

Change-Id: If391627d6823fd416417672e6b8bf4d91bd00c0e
diff --git a/voltha-adapter-openolt/values.yaml b/voltha-adapter-openolt/values.yaml
index 0bd2e31..a7c9f56 100644
--- a/voltha-adapter-openolt/values.yaml
+++ b/voltha-adapter-openolt/values.yaml
@@ -31,6 +31,7 @@
     timeout: "5s"
     heartbeat_check_interval: "15s"
     heartbeat_fail_interval: "31s"
+    check_onu_exist_on_discovery: false
 
   #enable OMCC encryption
   omcc_encryption: false
@@ -98,6 +99,7 @@
   kv_store_data_prefix: 'service/{{ .Values.global.stack_name }}_voltha'
   heartbeat_check_interval: '{{ .Values.global.adapter_open_olt.heartbeat_check_interval }}'
   heartbeat_fail_interval: '{{ .Values.global.adapter_open_olt.heartbeat_fail_interval }}'
+  check_onu_exist_on_discovery: '{{ .Values.global.adapter_open_olt.check_onu_exist_on_discovery }}' 
   rpc_timeout: '{{ .Values.global.rpc_timeout }}'
   endpoints:
     # core_endpoint: '{{ .Values.global.adapter_open_olt.core_endpoint }}'