unify code path for adding PKCS#11 providers

unify code path for adding PKCS#11 providers

Use existing wrapper for pkcs11h_addProvider to have arguments with
"magic values" for pkcs11-helper call in a central place.

Slot event argument to pkcs11h_addProvider has NOT been a boolean for
at least 15 years.
Luckily the default is PKCS11H_SLOTEVENT_METHOD_AUTO=0=FALSE.

Signed-off-by: Marc Becker <marc.becker@astos.de>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20221211190913.190-1-marc.becker@astos.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25642.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 8958a365479348c1500dee44e1a8b27e7e35a96f)