datatransfer: add a 10 minutes timeout when awaiting peer

Currently, when a file is sent, the peer needs to accept the transfer.
So, connections with this peer will be opened until the peer accepts or
not the file. Since the multi-device support, it's a problem because
the peer has to accept/refuse the transfer on each devices.

To avoid to leave unused connections while we are using the turn,
we need to close these connections. This patch add a timeout to
outgoing file transfers. So, after 10 minutes with the status
awaiting peer, the connection is closed and the transfer canceled.

NOTE: the peer will still see the awaiting_host status even if the
connection is closed, but it's a known bug and it will need a major
change of the blocking startNewFile function in FtpServer.

Change-Id: Ic6e3a2bfebad92cc5c64f5ac2355c3c3765752c9
Reviewed-by: Philippe Gorley <philippe.gorley@savoirfairelinux.com>