os/signal: TestAtomicStop fails on dragonflybsd

I'm seeing a fair amount of flakiness in TestAtomicStop on the dragonflybsd builder. Some recent examples:

https://build.golang.org/log/db81785148210a9493ea8327ebed605e5edb148f
https://build.golang.org/log/c6a7018d2725db0845999d53a48f0f30520c54b8
https://build.golang.org/log/0fdb68deb085ad75fd786b1e498e5f1bf8009269

Using Go 1.10 and a recent dragonfly build.

[dmitshur]

/cc @ianlancetaylor as owner of os/signal.

There is a lot of red for dragonfly/amd64 on build.golang.org on tip (almost half are fail). I've checked 5 pages worth and none of them are TestAtomicStop tests failing. Most of the failures are related to networking timeouts.

I'll close this since it doesn't seem to be an issue anymore, but we can re-open otherwise.

Sounds good. There does seem to be persistent but random problem connecting to the local test webservice, but I'm not having much luck tracking it down.