verify_ca_init: Reorder names to improve error message

[TinCanTech]

If verify_ca_init fails then the error message states that: 'serial is missing'. While this is true, it is not 'user friendly'.

Reorder the checks so that if verify_ca_init fails then the error message will "probably" state that: 'ca.crt is missing', which makes more sense if the CA has not been initialised.

Signed-off-by: Richard T Bonhomme [email protected]