random: Allow DRBG_REINIT before initialization.
* random/random-drbg.c (DRBG_DEFAULT_TYPE): New. (_drbg_init_internal): Set the default type if no type has been set before. (_gcry_rngdrbg_inititialize): Pass 0 for flags to use the default.
Without this change we can't call GCRYCTL_DRBG_REINIT before
intialization.
- Signed-off-by: Werner Koch <wk@gnupg.org>