Snapshot mode ALWAYS requires concurrent transaction for wal2json

When snapshot mode ALWAYS is in place then

• it queries current LSN
• streams changes from lastest seen LSN till the current LSN
• when the LSN coming from plugin matches or is large than the current LSN then th streaming is terminated and snapshot started

Unfortunately, the second condition can happen for wal2json plugin only when a concurrent transaction is exectued. The problem is that wal2json changes comes as a single event so there is not exact LSN match and the last streamed change will not reach the current LSN. This issue disappears as soon as another transaction is executed as the streaming processing moves pass the target LSN and starts the snapshot