tsmon: resolve hostname only by os.Hostname()
tsmon: resolve hostname only by os.Hostname()

On a mac, resolving with net.InterfaceAddrs() results in <name>.local
rather than the correct realm. And even that is flaky - sometimes it
resolves correctly.

BUG=617261
R=dsansome@chromium.org

Review-Url: https://codereview.chromium.org/2054083003

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go