These functions are a bit awkward to use for one-off file loads, as
suggested by the tls_clear_default_passwd_cb() logic. There was also
some historical mess with OpenSSL versions and either not having per-SSL
settings, having per-SSL settings but ignoring them, and requiring the
per-SSL settings.
Instead, loading the key with the lower-level functions seems a bit
tidier and also allows abstracting away trying both formats, one after
another.
Signed-off-by: David Benjamin <davidben@google.com>
63942cf0f3