crypto: fix default encoding of LazyTransform

PullRequest #5522 and #5500 described the change
of the default encoding into UTF8 in crypto functions.

This however was only changed for the non-streaming API.
The streaming API still used binary as the default encoding.

This commit will change the default streaming API encoding to UTF8
to make both APIs behave the same.

It will also add tests to validate the behavior.

Refs: https://github.com/nodejs/node/pull/5522
Refs: https://github.com/nodejs/node/pull/5500
PR-URL: https://github.com/nodejs/node/pull/8611


Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>