swarm: only request a connection when peer is detected if a sync is needed

fetched check the devices who has fetched since the last commit. With this file
we can detect if a device needs to fetch and if it's the case we start a connection.
cacheSipConnection will sync the conversations when called. This avoids the
daemon to connect too all contacts

Change-Id: Id85db09c3c0a6aa44dd48b3bbee5ed7e0a5d6b84