Test a 0 return from the ticket key callback

Test a 0 return from the ticket key callback

A 0 return from a ticket key callback should indicate that crypto parameters
are not currently available and that the handshake should continue without
generating/using the ticket.

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18990)