Data can re-appear after it's been deleted

[e-dard]

Whilst investigating #10052 I triggered another bug, which I initially thought was the source of #10052, but in the end isn't. The bug manifests itself as follows:

• You start up the sever with some data in the WAL.
• The data is added to the cache on startup.
• The cache snapshots the data to a TSM file (the cache is empty).
• You delete the data, e.g., via DROP SERIES or DROP MEASUREMENT.
• The data is deleted from the TSM files via tombstone markers.
• You restart the server - the data is back again.

You can reproduce via:

- startup influxdb

> insert cpu c=12
> select * from cpu
name: cpu
time                        c
----                        - 
2019-06-28T12:04:11.671819Z 12

- Shut down server
- Start it up, but with a much lower snapshot time so you don't need to wait..

$ INFLUXDB_DATA_CACHE_SNAPSHOT_WRITE_COLD_DURATION=10s  influxd

- *important*, wait for the cache to snapshot to a TSM file.

> drop measurement cpu
> select * from cpu
>

- restart server

> select * from cpu
name: cpu
time                        c
----                        - 
2019-06-28T12:04:11.671819Z 12

This affects all versions back to at least 1.5.3. I didn't test on earlier versions.

[e-dard]

Fixed via #14232