Add/Del lag_name_map item according to lag adding and removing (#1124)

The code is to add/del items in LAG_NAME_MAP_TABLE in COUNTERS_DB if a lag is added or removed.
The code need the below pull request:
#51 in Azure/sonic-py-swsssdk
read portchannel name from LAG_NAME_MAP_TABLE in COUNTERS_DB #51

For use of LAG_NAME_MAP_TABLE in COUNTERS_DB just like fdbshow.
I have create another pull request in Azure/sonic-utilities:
Show mac learned on lag interface #730

orchagent/portsorch.cpp

@@ -159,6 +159,12 @@ PortsOrch::PortsOrch(DBConnector *db, vector<table_name_with_pri_t> &tableNames)
     m_counter_db = shared_ptr<DBConnector>(new DBConnector("COUNTERS_DB", 0));
     m_counterTable = unique_ptr<Table>(new Table(m_counter_db.get(), COUNTERS_PORT_NAME_MAP));
 
+    m_counterLagTable = unique_ptr<Table>(new Table(m_counter_db.get(), COUNTERS_LAG_NAME_MAP));
+    FieldValueTuple tuple("", "");
+    vector<FieldValueTuple> defaultLagFv;
+    defaultLagFv.push_back(tuple);
+    m_counterLagTable->set("", defaultLagFv);
+
     /* Initialize port table */
     m_portTable = unique_ptr<Table>(new Table(db, APP_PORT_TABLE_NAME));
 
@@ -3202,6 +3208,11 @@ bool PortsOrch::addLag(string lag_alias)
     PortUpdate update = { lag, true };
     notify(SUBJECT_TYPE_PORT_CHANGE, static_cast<void *>(&update));
 
+    FieldValueTuple tuple(lag_alias, sai_serialize_object_id(lag_id));
+    vector<FieldValueTuple> fields;
+    fields.push_back(tuple);
+    m_counterLagTable->set("", fields);
+
     return true;
 }
 
@@ -3246,6 +3257,8 @@ bool PortsOrch::removeLag(Port lag)
     PortUpdate update = { lag, false };
     notify(SUBJECT_TYPE_PORT_CHANGE, static_cast<void *>(&update));
 
+    m_counterLagTable->hdel("", lag.m_alias);
+
     return true;
 }
 

orchagent/portsorch.h

@@ -93,6 +93,7 @@ class PortsOrch : public Orch, public Subject
     bool removeSubPort(const string &alias);
 private:
     unique_ptr<Table> m_counterTable;
+    unique_ptr<Table> m_counterLagTable;
     unique_ptr<Table> m_portTable;
     unique_ptr<Table> m_queueTable;
     unique_ptr<Table> m_queuePortTable;