zap never closes open sinks except its own tests. This behaviour
prevents TestHandleLoggingParams from successful cleanup because
temp log output file can't be closed due to the following error:
```
TempDir RemoveAll cleanup: remove C:\\Users\\Anna\\AppData\\Local\\Temp\\TestHandleLoggingParams_debug5796883
33\\001\\file.log: The process cannot access the file because it is being used by another process.
```
So this tremendous cludge is made mosetly for our testing code.
It is not for concurrent usage (we don't have cases of
multithreaded access to logger output sink).
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