use HTTP 2.0

[sherlock1982]

Fixes #5209

[bgavrilMS]

Hi @sherlock1982 - there is a bit more to it because I discovered that some internal endpoints don't yet support HTTP/2.0

Here is a PR to fix this issue - #5314, which also includes tests

As such, I'm going to close yours.

[sherlock1982]

It's ok. But just to let you know setting HTTP 2.0 doesn't mean 2.0 only. It means 2.0 or less if not supported.
If we can do it different way, optional way - of course that would be better