audit: do not remove file installed by netplug

audit: do not remove file installed by netplug

The package recipe uses a post-install hook to remove useless files from
$(TARGET_DIR)/etc/rc.d/init.d and $(TARGET_DIR)/etc/sysconfig. This may
damage packages that install useful files on those directories (such as
netplug, which installs $(TARGET_DIR)/etc/rc.d/init.d/netplugd).

In the future[1] we will reorganize the init scripts and possibly get
rid of /etc/rc.d and /etc/sysconfig but for the moment let's restrict
the file removal to those installed by audit.

1. http://lists.busybox.net/pipermail/buildroot/2018-May/221549.html

Signed-off-by: Carlos Santos <casantos@datacom.com.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>