connectionmanager: fallback on DHT if peer doesn't answer

If the peer has a connectivityChange, this can take time before
detecting the actual disconnection. This patch fallback on the DHT
if the peer doesn't answer on the cached link (the peer can be
disconnected at this point)

Change-Id: I3ce91b3f59b393c95741d13ae4e5549d203967b4
Gitlab: #209