t_client.sh.in: Use printf instead of echo -e

t_client.sh.in: Use printf instead of echo -e

In some shells the echo builtin doesn't interpret -e as
an argument, it just outputs it as a string.

Examples for shells I have observed this with are dash on
Ubuntu and /bin/sh on macOS.

Use printf instead which should have better consistency
across shells and operating systems.

Change-Id: I746bd8c0fa3496d23569cde496438fc4189600fe
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1753
Message-Id: <20260809153046.14738-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg38258.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>