[test] Convert unhandledRejection to uncaughtException

[danielpeintner]

As mentioned in #1298 by @relu91 (see here #1298 (comment)) mocha ignores the new nodejs mechanism of reporting async unhandled exceptions.

We need to set
mocha --unhandled-rejections=strict --require ts-node/register --extension ts
in all package.json files.

Doing so for binding-http shows already some issues.
see #1298 (comment)

plus: we also might want to rework the test introduced in #1298 by simply doing something like
(await text(data.body)).should.eql("Test event");