Add MESSAGE_INTEGRITY to indications

[OrangeDog]

RFC 5389 Section 10.1.1

For a request or indication message, the agent MUST include the USERNAME and MESSAGE-INTEGRITY attributes in the message.

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.

[OrangeDog]

CLA signed.