using TreeMaps in JobTracker

[Vivek Ratan]

The JT has a number of Map member variables, and I noticed that it uses
TreeMaps for most, if not all, of them. I also noticed that these member
variables are pretty much used for 'puts' and 'gets'. Given that there
is no need for sorted iteration, and the JT doesn't even iterate over
any of these maps, shouldn't it be better to use HashMaps?