cmd/gopls/forward: use select instead of empty for

[pwaller]

An empty for loop body results in a CPU spinning at 100% CPU.

select {} is more friendly to battery life.

/cc @stamblerre

[gopherbot]

This PR (HEAD: 1baf584) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/tools/+/161837 to see it.

Tip: You can toggle comments from me using the comments slash command (e.g. /comments off)
See the Wiki page for more info

[gopherbot]

Message from Ian Cottrell:

Patch Set 1: Code-Review-1

Hi,
There is nothing wrong with this change, but in
https://go-review.googlesource.com/c/tools/+/161658
I am totally removing this file, and integrating the functionality directly into gopls.
The new version does not use the busy loop.

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/161837.
After addressing review feedback, remember to publish your drafts!