Fix broken archive feature

Summary: - Remove replies attribute when change the archive status of a message

Test Plan:
 - go to #messages/list/all
 - click on `Archive` to archive a message
 - See an alert show `Message has been archived` and message moved to the archived list

Reviewers: shadowhand, rjmackay

Reviewed By: shadowhand, rjmackay

Subscribers: shadowhand, srutto, lkamau

Maniphest Tasks: T452

Differential Revision: https://phabricator.ushahidi.com/D277