SEBA-588 Fix key format in flow_extract_info()

Change-Id: Iab1d7aaba4ce4d7b0666ccc00ba16be37a4c0861
diff --git a/voltha/adapters/openolt/openolt_platform.py b/voltha/adapters/openolt/openolt_platform.py
index d592fd9..1291ce9 100644
--- a/voltha/adapters/openolt/openolt_platform.py
+++ b/voltha/adapters/openolt/openolt_platform.py
@@ -178,4 +178,4 @@
         onu_id = self.onu_id_from_uni_port_num(uni_port_no)
         uni_id = self.uni_id_from_port_num(uni_port_no)
 
-        return pon_intf, onu_id, uni_id
+        return int(pon_intf), int(onu_id), int(uni_id)