In the case of caching TSI bitmaps belonging to immutable .tsi files,
the underlying bitset data can be mmapped. It is possible, though rare,
for this data to be unmapped (e.g., via a TSI compaction) but for the
cached bitmap to be subsequently read. This leads to a segfault.
This only happens when copy-on-write is set to true on the roaring
bitmap, because in that case only the internal pointers are cloned.
This change will reduce the TSI cache performance by around 10%, which I
have deemed to account for only a few microseconds typically.
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
```
Stuart Carnie
Edd Robinson
Jacob Marble
Mark Rushakoff
Jeff Wendling