Send Jingle source parameters with the correct namespace

[jbg]

Ref: jitsi/jitsi-xmpp-extensions#82

This shouldn't be merged (and tests will fail) until jitsi-xmpp-extensions is updated.

[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 :(.