Run all Go tests with flag -race

[programmer04]

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

Running

go test -race -short ./...

on current master finishes without any errors, so it's a great opportunity to add -race flag to all invocation of tests and closes #7729 🎉

In the Makefile for all invocation of tests if run not with GOARCH=386 flag (Go race detector works only on 64 bit architectures) flag -race is added.

[ssoroka]

hmm. apparently not supported on 386 architectures.

[programmer04]

@ssoroka I'm modifying makefile to not run them with the flag -race for GOARCH=386

[danielnelson]

Let's make this a new phony target test-race and run it via Circle and Appveyor.

[ssoroka]

looks like there's a race affecting windows only.
plugins/inputs/ping/ping_windows.go
remove this at line 16:

	if p.Count < 1 {
		p.Count = 1
	}

It's redundant as it's checked on init, and causing the race condition.

[danielnelson]

Another option instead of the phony target is to do nothing in the Makefile, but set GOFLAGS="$GOFLAGS -race" in the CI configuration. I'm not 100% sure if this flag is honored though, would need tested.

[programmer04]

I didn't have time and Win setup to check it in detail. On other systems, it works fine 🙂
@ssoroka I applied your suggestion and tests pass on Windows too. So on every platform except 386 all tests are run with -race enabled. Thanks for guidance 🙂