cve-update-nvd2-native: Tweak to work better with NFS DL_DIR

cve-update-nvd2-native: Tweak to work better with NFS DL_DIR

After much debugging, the corruption issues on the autobuilder appear to
be due to the way sqlite accesses database files. It doesn't change the
file timestamp after making changes, which for reasons unknown, confuses
NFS. As soon as the file is touched, NFS becomes fine again accross the
whole cluster, as if by magic.

We could try and debug further but putting a "touch" call into the code
is easy and harmless. Lets hope this removes this annoying source of
errors.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>