This commit adds the `.tss` files generated for TSM statistics to
the `FileObserver` so that package users can be notified when new
stats files are created and removed.
This commit replaces an `os.OpenFile()` call with an `os.Create()`
call which drops `O_EXCL` for `O_TRUNC` since `.tss` files are only
created after `.tsm` files so lingering temporary files are safe to
overwrite.
The tsdb/tsm1 package was one of the test suites that took the longest
to run in platform with go test -short. The rule of thumb on the Go
project is that short mode should skip any individual test that takes
longer than one second. This change skips two such tests, and it
eliminates a string concatenation loop in two other tests, so that they
report completion in "0.00s" rather than about 0.94s, on my machine.
These cumulative changes take `go test -short ./tsdb/tsm1` from about 14
seconds to about 7 seconds on my machine.
And add a test to cover that.
The data race would look roughly like:
```
WARNING: DATA RACE
Write at 0x00c000024e18 by goroutine 8:
github.com/RoaringBitmap/roaring.(*roaringArray).markAllAsNeedingCopyOnWrite()
/Users/mr/go/pkg/mod/github.com/!roaring!bitmap/roaring@v0.4.16/roaringarray.go:881 +0x6b
github.com/RoaringBitmap/roaring.(*roaringArray).clone()
/Users/mr/go/pkg/mod/github.com/!roaring!bitmap/roaring@v0.4.16/roaringarray.go:266 +0x808
github.com/RoaringBitmap/roaring.(*Bitmap).Clone()
/Users/mr/go/pkg/mod/github.com/!roaring!bitmap/roaring@v0.4.16/roaring.go:385 +0x58
github.com/influxdata/platform/tsdb.(*SeriesIDSet).CloneNoLock()
/Users/mr/go/src/github.com/influxdata/platform/tsdb/series_set.go:229 +0x73
github.com/influxdata/platform/tsdb.(*SeriesIDSet).Clone()
Previous write at 0x00c000024e18 by goroutine 7:
github.com/RoaringBitmap/roaring.(*roaringArray).markAllAsNeedingCopyOnWrite()
/Users/mr/go/pkg/mod/github.com/!roaring!bitmap/roaring@v0.4.16/roaringarray.go:881 +0x6b
github.com/RoaringBitmap/roaring.(*roaringArray).clone()
/Users/mr/go/pkg/mod/github.com/!roaring!bitmap/roaring@v0.4.16/roaringarray.go:266 +0x808
github.com/RoaringBitmap/roaring.(*Bitmap).Clone()
/Users/mr/go/pkg/mod/github.com/!roaring!bitmap/roaring@v0.4.16/roaring.go:385 +0x58
github.com/influxdata/platform/tsdb.(*SeriesIDSet).CloneNoLock()
/Users/mr/go/src/github.com/influxdata/platform/tsdb/series_set.go:229 +0x73
github.com/influxdata/platform/tsdb.(*SeriesIDSet).Clone()
/Users/mr/go/src/github.com/influxdata/platform/tsdb/series_set.go:223 +0x7b
```