avahi-autoipd: fix issue with repeated builds

The avahi-autoipd target install step adds /var/lib/avahi-autoipd as a
symlink to /tmp/avahi-autoipd, which is fine, except if your /var/lib is
already a symlink to /tmp (E.G. like the default target_skeleton is).

If that's the case, then you end up adding a /tmp/avahi-autoipd symlink
pointing to itself, causing subsequent builds to fail
(Too many levels of symbolic links in the ln -sf call). Fix it by simply
first removing the symlink if it's there.

package/avahi/avahi.mk

@@ -158,6 +158,7 @@ $(TARGET_DIR)/usr/sbin/avahi-autoipd: $(AVAHI_DIR)/.installed
 	chmod 0755 $(TARGET_DIR)/usr/share/udhcpc/default.script
 	cp -af package/avahi/S05avahi-setup.sh $(TARGET_DIR)/etc/init.d/
 	cp $(STAGING_DIR)/usr/sbin/avahi-autoipd $@
+	rm -f $(TARGET_DIR)/var/lib/avahi-autoipd
 	ln -sf /tmp/avahi-autoipd $(TARGET_DIR)/var/lib/avahi-autoipd
 	$(STRIPCMD) $(STRIP_STRIP_UNNEEDED) $@