Update evp_test to make sure passing partial block to "Update" is ok

The previous commit fixed a bug where a partial block had been passed to
an "Update" function and it wasn't properly handled. We should catch this
type of error in evp_test.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2275)