Add a PKCS12 test to check with one input cert we get one output cert

Add a PKCS12 test to check with one input cert we get one output cert

Following on from the regression in issue #15983, add a test that with
one input cert, we get one cert in the pkcs12 file, and that it has the
expected friendlyName.

Reviewed-by: David von Oheimb <david.von.oheimb@siemens.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16001)