Use exponential backoff for caching in tls_authentication_status

Use exponential backoff for caching in tls_authentication_status

The caching in tls_authentication_status broke the quick reaction to
authentication status in the code paths that did not do caching like
PUSH_REQUEST reply code path.

This patch introduces exponential backoff for the caching so we still
retain the quick reaction while still keeping the benefit of caching.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20210510131356.968965-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22327.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>