The broadcast_transaction_with_callback API does not return operation result in version test-6.0.1

Bug Description

Starting from the test-6.0.0 version on testnet, the broadcast_transaction_with_callback API no longer returns operation results.

Reported by @syalon.

Impacts Describe which portion(s) of BitShares Core may be impacted by this bug. Please tick at least one box.

[x] API (the application programming interface)
[ ] Build (the build process or something prior to compiled code)
[ ] CLI (the command line wallet)
[ ] Deployment (the deployment process after building such as Docker, Travis, etc.)
[ ] DEX (the Decentralized EXchange, market engine, etc.)
[ ] P2P (the peer-to-peer network for transaction/block propagation)
[ ] Performance (system or user efficiency, etc.)
[ ] Protocol (the blockchain logic, consensus, validation, etc.)
[ ] Security (the security of system or user data, etc.)
[ ] UX (the User Experience)
[ ] Other (please add below)

Steps To Reproduce Steps to reproduce the behavior (example outlined below):

Execute API call broadcast_transaction_with_callback
Using JSON payload '...'
Received response {"id":"73a06780e64d317df8feadf59b738becc5d9b26c","block_num":2,"trx_num":2,"trx":{"ref_block_num":1,"ref_block_prefix":3137354359,"expiration":"2015-05-15T14:27:45","operations":[[0,{"fee":{"amount":0,"asset_id":"1.3.0"},"from":"1.2.16","to":"1.2.0","amount":{"amount":1,"asset_id":"1.3.0"},"extensions":[]}]],"extensions":[],"signatures":["1f3f4ab1ecdadb2635be42a9aa3bd0fa5a7c49945db4bb88eaf8b17374cbefa0535780a1ae402e1d31281fa2f1a2102f66195d6e431a95a456d58f03501f79752c"],"operation_results":[[0,{}]]}}. In the response, operation_results is empty.

Expected Behavior It is expected that operation_results is non-empty.

Host Environment Please provide details about the host environment. Much of this information can be found running: witness_node --version.

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