Switches from using JitsiConference.isJvbConnectionInterrupted
flag to peerconnection's ICE state. The interrupted
flag is not set if the connection fails initially.

Because it's possible to go back from ICE FAILED state to CONNECTED it's
better to give it some time until the XMPP connection recovers and only
if they ICE does not recover in time send the ICE failed notification
to Jicofo. It's done by sending a ping to the XMPP server and checking
the ICE after 2 seconds past the ping successful response.