random: Change initial extra seeding from 2400 bits to 128 bits.
* random/random-csprng.c (read_pool): Reduce initial seeding.
See discussion starting at
https://lists.gnupg.org/pipermail/gnupg-devel/2015-April/029750.html
and also in May.
- Signed-off-by: Werner Koch <wk@gnupg.org>