Fix side effect of record modified affecting the next in line handler.

[saffih]

The issue
Hoover processing has a side effect modifying the LogRecord "msg" field.

The existing code handling a Log Record having a dict data as message is as follows:
convert the dict into json,
update the record.msg to reference that json ( modifying the original record)
delegating that record

Some OTHER log handler expecting the message as dict would fail,
It takes the record.msg which should have been a dict and since hoover has changed that, it is now a json.

The fix
Hoover use a modified shallow copy instead of actually modifying the log record.

Using python shallow clone copy.copy which is modified and used by hoover. The original LogRecord does not change.