All mined blocks are Orphaned
Since the most recent merges, it seems all mined block are orphaned.
```
$ grep 'MINED A BLOCK' data/testnet/logs/monero-pool.log 
2019-08-25 16:16:31 INFO  src/pool.c:2404: +++ MINED A BLOCK +++
2019-08-25 16:21:12 INFO  src/pool.c:2404: +++ MINED A BLOCK +++
2019-08-25 16:22:33 INFO  src/pool.c:2404: +++ MINED A BLOCK +++
2019-08-25 16:28:00 INFO  src/pool.c:2404: +++ MINED A BLOCK +++
```
Compared to:
```
$ grep 'Orphaned block' data/testnet/logs/monero-pool.log 
2019-08-25 16:16:31 DEBUG src/pool.c:759: Orphaned block at height 1285175
2019-08-25 16:18:37 DEBUG src/pool.c:759: Orphaned block at height 1285176
2019-08-25 16:18:39 DEBUG src/pool.c:759: Orphaned block at height 1285177
2019-08-25 16:21:12 DEBUG src/pool.c:759: Orphaned block at height 1285178
2019-08-25 16:27:09 DEBUG src/pool.c:759: Orphaned block at height 1285180
```
