jsonrpc: Properly implement connection timeout.

jsonrpc: Properly implement connection timeout.

jsonrpc_session_connect() indirectly called reconnect_disconnected(), which
told the reconnect object that the connection had failed, before it told it
that the connection attempt had started.  When the connection didn't
complete immediately, this caused the connection to time out immediately,
without any backoff.

Reported by Jeremy Stribling.