Use smaller envInfo.os

We currently send entire `userAgent` as the `envInfo.os` value during `/authenticate` requests to Controller.

Instead, let's send only the last "_portion_" of the UA.

e.g., instead of:

`5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36
`
let's try to send only:

`Chrome/87.0.4280.88`