Fix verify algorithm.

Disable loop checking when we retry verification with an alternative path.
This fixes the case where an intermediate CA is explicitly trusted and part
of the untrusted certificate list. By disabling loop checking for this case
the untrusted CA can be replaced by the explicitly trusted case and
verification will succeed.

Signed-off-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit e5991ec5

)

Reviewed-by: Rich Salz <rsalz@openssl.org>