random: Add finalizer for rndjent.
* random/rand-internal.h (_gcry_rndjent_fini): New. * random/rndjent.c (_gcry_rndjent_fini): New. * random/rndlinux.c (_gcry_rndlinux_gather_random): Call the finalizer when GCRYCTL_CLOSE_RANDOM_DEVICE.
- GnuPG-bug-id: T3731
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>