r1498: (merge from 3.0)
Rework our random number generation system.
On systems with /dev/urandom, this avoids a change to secrets.tdb for every fork().
For other systems, we now only re-seed after a fork, and on startup.
No need to do it per-operation. This removes the 'need_reseed'
parameter from generate_random_buffer().
This also requires that we start the secrets subsystem, as that is
where the reseed value is stored, for systems without /dev/urandom.
In order to aviod identical streams in forked children, the random
state is re-initialised after the fork(), at the same point were we do
that to the tdbs.
Andrew Bartlett
(This used to be commit
b97d3cb2efd68310b1aea8a3ac40a64979c8cdae)