info: Reduce delay between messages

The info service takes a long time to populate its state after a restart, in
particular on production scale systems.

This patch reduces the delay between queries. The overall frequency is not
increased, but the delay between two queries is reduced to 100 ms (from 2, 5,
or 10 seconds, depending on the query). As these queries are relatively
light-weight, 100 ms should be plenty to keep the message passing overhead
down.

I request backport to 2.10 as we always have issues with our Nagios probes
after a restart.

Target: trunk
Request: 2.11
Request: 2.10
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: https://rb.dcache.org/r/7535/