Update lgd comment endpoint - support multiple comments

[dglemos]

Ticket: G2P-368

Endpoint: lgd/<str:stable_id>/comment/
Input data:

{
                    "comments": [
                        {
                            "comment": "This is a comment",
                            "is_public": 1
                        },
                        {
                            "comment": "This is another comment",
                            "is_public": 0
                        }
                    ]
                }

[seeta-ramaraju]

Add a try/catch block to catch error during save action