man: extend --persist-tun section

man: extend --persist-tun section

The current persist-tun section has no mention of
retaining IP/routes and its potential usage in traffic
leaking protection.

Spell this out to allow the user to better understand
when this option can play an important role.

Change-Id: I6816f61b308ca9f6d1f9f687a6dc8e0aa2d044e0
Signed-off-by: Antonio Quartulli <antonio@mandelbit.com>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20250129094125.13420-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg30684.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>