Avoid duplicate message in history on re-connect in (v3)

[sushmi21]

This PR prevents duplicate messages in chat history by not prepending messages to the message history on re-connect.

Success Criteria:

• Reconnecting behaviour should remain unaffected. Reconnect screen should appear, chat history should not disappear
• In chat history, redunant messages should not appear on re-connecting
• please do a thorough testing to avoid regression
• When a session id is defined in index.html, then the chat history should be restored even after page reload
• When session id is not defined in index.htm, then reloding the page should clear the chat history

How to test:

• Send a message to the bot and wait for a response.
• Now, in browser console, select network to 'Offline' or simply disconnect your PC's wifi
• After few minutes, put your network to 'No throttling' or connect the wifi back.
• Check SC