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

This reverts commit 21ebca9.

Author: qiluo-msft

src/swsssdk/port_util.py

@@ -49,9 +49,6 @@ 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()}