Remove Deprecated Dockers

It is my understanding the following dockers are deprecated (used in SONiC v1, but no longer used in v2) and can be removed. Just wanted to add an issue here for discussion/confirmation:

- docker-lldp
- docker-mlnx-sswsyncd
- docker-mlnx-sswsyncd-rpc
- docker-snmp
- docker-sswsyncd