Adding metadata match criterion to the classifier of the openolt_flow_mgr

Change-Id: Ic3faca75920cb465f1738ae6f6c4765fd72b190e
(cherry picked from commit 7bcb25c0d94ccf6a50b273a3e1752fa22e4c113e)
diff --git a/voltha/adapters/openolt/openolt_flow_mgr.py b/voltha/adapters/openolt/openolt_flow_mgr.py
index b00a60f..1cc58db 100644
--- a/voltha/adapters/openolt/openolt_flow_mgr.py
+++ b/voltha/adapters/openolt/openolt_flow_mgr.py
@@ -165,6 +165,8 @@
                 classifier_info[IPV4_SRC] = field.ipv4_src
                 self.log.debug('field-type-ipv4-src',
                                ipv4_dst=classifier_info[IPV4_SRC])
+            elif field.type == fd.METADATA:
+                pass
             else:
                 raise NotImplementedError('field.type={}'.format(
                     field.type))