SPY-118: Include more information in the timeout message.

Note: there isn't coherency in this commit, but that is somewhat
intentional to not take on the overhead. The message is on the user's
thread and the updates of last read are on the IO thread.

Change-Id: Ia0a7cdc9296ea1de34d23a4d67c8a6bd1db7ba93
Reviewed-on: http://review.couchbase.org/26101
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>