Serialization/Deserialization of Transaction object resets fee to 1000.

### Subject of the issue

Fix Transaction Java serialization to preserve the fee value. In group transactions, fees can be paid by a single party in the transaction, so it is important to be able to specify a 0 transaction fee for other parties.

### Your environment
Java SDK v 1.14.0

### Steps to reproduce

1. Set the Transaction fee to 0.
2. Serialize and deserialize the transaction.
3. Note that the transaction fee is 1000, rather than 0.

### Expected behavior

The transaction fee should remain what was set.

### Actual behavior

The transaction fee is reset to 1000 after serialization/deserialization, the set value is lost.