pf: clean up temporary files if plugin init fails

pf: clean up temporary files if plugin init fails

close_instance() tries to remove the file in c2.pf.filename, but that only
works if we actually set that if we fail.  So, set that filename as soon
as we know we've created the file.

Signed-off-by: Steffan Karger <steffan.karger@fox-it.com>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20171101220342.14648-2-steffan@karger.me>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg15705.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>