Reduce initial and ongoing RendPostPeriod for SOS
Initial descriptor uploads
Hidden services hide their start times by uploading their first descriptor after:
now + rendinitialpostdelay + crypto_rand_int(2*rendpostperiod);
which is currently 30 + rand(2*600) seconds minimum.
A RSOS doesn't need to hide its startup time, but should avoid a thundering herd. So we could change it to:
now + rendinitialpostdelay + crypto_rand_int(1*rendpostperiod);
(Or perhaps some fraction of RendPostPeriod, or perhaps a constant like 60 seconds.)
Ongoing descriptor uploads
If a RSOS site implements failover or high availability, it may need to post descriptors more often than the current minimum RendPostPeriod of 10 minutes.
For example, if a RSOS goes down, and another instance should replace it within 30 seconds, it would need: 600/30 = 20 redundant instances
Instead, if we want a small number of instances, say 4: 30 * 4 = 120 second RendPostPeriod. (This also helps with the initial post period above.)
This is perhaps mitigated by multiple HSDirs, with some having descriptors from one replica, and some from the other. (But this is not guaranteed - one replica could have just uploaded all the HSDirs, then gone down.)
This also needs a proposal update.