Upgrade Golang to 1.17.1

[notnoop]

Also, ran gofmt on all files, mostly to handle the new build directives noted in Go 1.17 release notes

//go:build lines

The go command now understands //go:build lines and prefers them over // +build lines. The new syntax uses boolean expressions, just like Go, and should be less error-prone. As of this release, the new syntax is fully supported, and all Go files should be updated to have both forms with the same meaning. To aid in migration, gofmt now automatically synchronizes the two forms. For more details on the syntax and migration plan, see https://golang.org/design/draft-gobuild.

https://golang.org/doc/go1.17 .

gofmt changed few other constructs, namely initializations. I ran find . -type f -name '*.go' -exec gofmt -s -w {} \;.

Closes #11153

[schmichael]

Thanks! Looks like all of the changes shouldn't make CI or builds unhappy for Nomad v1.0.x (Go 1.15) if they get pulled in by a backport. Was a little worried about that, but I should have trusted the Go team to do a good job of taking backward compatibility into consideration.

[schmichael]

Oops could use a mention of 1.2.0 -> 1.17 here: https://github.com/hashicorp/nomad/blob/main/contributing/golang.md

[schmichael]

Oops, don't forget a changelog like:

• build: Updated to Go 1.15.13 [GH-10734]

[github-actions]

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