libtls: Replace expired certificates for unit tests

libtls: Replace expired certificates for unit tests

Only the tests with client authentication failed, the client accepted
the trusted self-signed certificate even when it was expired.  On the
server the lookup (based on the pre-configured SAN) first found the ECDSA
cert, which it dismissed for the RSA authentication the client used, and
since only the first "pretrusted" cert is considered the following RSA
cert was verified more thoroughly.
The lookup on the client always uses the full DN of the server certificate
not the pre-configured identity so it found the correct certificate on
the first try.