Use non-default mgm key instead of default in PIV generate cert tests
Use non-default mgm key instead of default in PIV generate cert tests

In this case the management key is actually required as a commandline
argument, whereas in the default case it's implicitly set to the default
management key because standard input is empty. Thus the previous form
of these tests would "magically" work even without the mgm key argument.

Yubico/yubikey-manager,Yubico/yubikey-manager