Writing to "/tmp/nsswitch.conf" leads to a race condition if two
copies of the postinst are running simultaneously. Fix this by
modifying /etc/nsswitch.conf in place using sed -i. Also make the
same change to the prerm for consistency although the race will not
occur here in practice.
Signed-off-by: Phil Blundell <philb@gnu.org> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
