test: improve crypto HMAC test assertions

Fixes argument order for assertions and makes their failure messages
more descriptive and easier to debug.

PR-URL: https://github.com/nodejs/node/pull/16026


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Lance Ball <lball@redhat.com>