Return value of `BeforeConvertCallback.onBeforeConvert()` is not used when actually saving

[idemockle]

When I create a copy of the entity passed into BeforeConvertCallback.onBeforeConvert(), make changes to the copy, then return the copy, the original entity object is used to generate the insert query instead of the modified copy. I would expect the copy to be used instead, otherwise it's hard for me to see why onBeforeConvert() would return a value.

[mp911de]

This is a bug in the CassandraTemplate and AsyncCassandraTemplate classes where the insert of non-versioned entities is affected.