Improve data key id not found error message

Improve data key id not found error message

With delayed data key generation now with deferred auth, NCP and similar
mechanism the "TLS Error: local/remote TLS keys are out of sync" is shown
much too frequent and confuses a lot of people.

This also removes the dead code of printing multi not ready keys and
replace it with an assert.

Factor out printing of error messages into an extra function to make
the code easier to understand and also to only call into that function
in the case that a key is not found and avoid the overhead.

Patch v2: fix comparing key_id to state value, improve message
Patch v3: also take key_id into account

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20220914172527.2661529-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25212.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>