[Notifications] Notifications that require acceptance should send an update status to clients in case of being updated at server directly

[mcastroSG]

Expected behaviour

Those notifications that require acceptance as Federated Sharing files could be "answered" at server browser , but in case we "answer" this notification and update should be sent to the clients to delete this notification.

Actual behaviour

In case we answer this notification at server browser, notification remains at clients, waiting for answer.

Steps to reproduce

1. As user1 connected to server1 share using federated sharing a file with a user from other server
2. As user2 connect desktop client to server2, and check that a new notification is shown at server activity tab.
3. As user 2 connect to server browser and "answer" this notification.

Server configuration

Server OS: Ubuntu
Server version: 9.1.0 Alpha

Client configuration

Client OS : OS X El capitán 10.11.4
Client Version: Version 2.2.0-nightly20160504 (build 3331)

Related to https://github.com/owncloud/client/issues/3733

[guruz]

FYI @nickvergessen @dragotin

[nickvergessen]

Should be done, but we don't live-listen to it, so it will disappear on the next polling of the client ( I think default is 5 minutes)