Review timer.num_threads configs in JGroups protocol stacks

Per Bela:

I assume you are aware of the fact that we don't use the jgroups.timer.num_threads system property to configure the number of timer threads. Instead, property "timer.num_threads" is configured per instance of TP. Of course, in a shared transport, there's only 1 timer thread pool (as discussed in 5.5 http://www.jgroups.org/javagroupsnew/docs/manual/html/user-advanced.html#d0e2680), but you probably need to increase the default of 4 in case we have a shared transport with multiple channels on top of it. N * 4 would be a simple approach, where N is the max number of channels you have in AS. However, since not all channels are high-perf, you want to find tune this value, possibly to a lower number.