Revert "Revert "read portchannel name from LAG_NAME_MAP_TABLE in COUNTERS_DB (sonic-net#51)" (sonic-net#57)" (sonic-net#64)

This reverts commit 022d8fb.

Add sonic-net#51 back in by reverting sonic-net#57, in because issues should be addressed by the merge of sonic-net/sonic-swss#1124

Author: jleveque

src/swsssdk/port_util.py

@@ -49,6 +49,9 @@ def get_interface_oid_map(db):
     """
     db.connect('COUNTERS_DB')
     if_name_map = db.get_all('COUNTERS_DB', 'COUNTERS_PORT_NAME_MAP', blocking=True)
+    if_lag_name_map = db.get_all('COUNTERS_DB', 'COUNTERS_LAG_NAME_MAP', blocking=True)
+    if_name_map.update(if_lag_name_map)
+
     oid_pfx = len("oid:0x")
     if_name_map = {if_name: sai_oid[oid_pfx:] for if_name, sai_oid in if_name_map.items()}