[lldpmgrd] Don't log error message for outdated redis event

[vivekrnv]

Why I did it

When a redis event quickly gets outdated during port breakout, error logs like this are seen

Mar  8 01:43:26.011724 r-leopard-56 INFO ConfigMgmt: Write in DB: {'PORT': {'Ethernet64': {'admin_status': 'down'}, 'Ethernet68': {'admin_status': 'down'}}}
Mar  8 01:43:26.012565 r-leopard-56 INFO ConfigMgmt: Writing in Config DB
Mar  8 01:43:26.013468 r-leopard-56 INFO ConfigMgmt: Write in DB: {'PORT': {'Ethernet64': None, 'Ethernet68': None}, 'INTERFACE': None}
Mar  8 01:43:26.018095 r-leopard-56 NOTICE swss#portmgrd: :- doTask: Configure Ethernet64 admin status to down
Mar  8 01:43:26.018309 r-leopard-56 NOTICE swss#portmgrd: :- doTask: Delete Port: Ethernet64
Mar  8 01:43:26.018641 r-leopard-56 NOTICE lldp#lldpmgrd[32]: :- pops: Miss table key PORT_TABLE:Ethernet64, possibly outdated
Mar  8 01:43:26.018654 r-leopard-56 ERR lldp#lldpmgrd[32]: unknown operation ''

How I did it

Only log the error when the op is not empty and not one of ("SET" & "DEL" )

How to verify it

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202211

Description for the changelog

Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)