CLI push - change behavior pushing TM with same content

[enricoschuetz]

Current behavior:

When pushing a TM that already exists with the same content and version,
the push is rejected if the same TM (same digest) has the latest timestamp in history. (OK).

When pushing a TM that already exists with the same content and version,
but the same TM (same digest) has not the latest timestamp in history, then the push is simply accepted.

Although it makes sense to "reset" a specific content from point of timestamp, this could be a bit confusing
when the behavior differs.

Expected behavior (proposal):

When pushing a TM that already exists with the same content and version,
the push is default rejected.

Only by passing a --force flag, the TM with same content and version can be pushed,
so it has the latest timestamp in history.