[LLDP]: Modify OID index of LLDPRemTableUpdater MIB (#155)

* [LLDP]: LLDPRemTableUpdater index in OID is a tuple of
(if index, remote time mark, remote device index).
In case of multi-asic platform, when querying this MIB it can happen
that same if index result is seen in SNMP walk, with a different
remote time mark. To avoid showing same if index result in the
result, set remote time mark to 0.
* Add code comment.

src/sonic_ax_impl/mibs/ieee802_1ab.py

@@ -430,7 +430,12 @@ def update_data(self):
  if not lldp_kvs:
  continue
  try:
- time_mark = int(lldp_kvs[b'lldp_rem_time_mark'])
+ # OID index for this MIB consists of remote time mark, if_oid, remote_index.
+ # For multi-asic platform, it can happen that same interface index result 
+ # is seen in SNMP walk, with a different remote time mark.
+ # To avoid repeating the data of same interface index with different remote 
+ # time mark, remote time mark is made as 0 in the OID indexing.
+ time_mark = 0
  remote_index = int(lldp_kvs[b'lldp_rem_index'])
  self.if_range.append((time_mark,
  if_oid,