runtime: make GC runtime stats test run on GCE #8634
In https://code.google.com/p/go/source/detail?r=ec6629ef3dae19 I removed part of a test that Dmitry liked because it doesn't run on GCE (which only has ~1ms timers apparently). This bug is about restoring the test somehow. We could make it a -short test (so it's skipped on builders, but runs on our machiens). Or try the test first and if we get a 0ns pause, then generate a lot of garbage and try for a >= 1 ms GC pause, which is measurable on Windows (physical hardware) and GCE (any OS).