Oops, require cloud of 3 for KMeansTest
First cut I/O profiling; TCP, NFS, ICE

Crucially missing HDFS & S3 because they do not support NIO operations.
New Admin page Cluster I/O.  Reports r/w effective and peak bandwidth
for the last 1sec/2/10/30/60/120/600.  Data is recorded in the Timeline
ring buffer, so under load it will 'ageout' quicker than the promised
10-min interval.
Fix logging '%' chars bug

Also survive LOG_KEY appearing during junit testing, confusing
the leaking key check