If a tx is marked as failed (because it never shows up in the
daemon's pool), its key images get reset back to unspent so they
can be used in future txs.
If the tx re-enters the daemon's pool (e.g. it's removed from the
pool and then relayed back), then the wallet incorrectly maintains
that the tx's key images are unspent.
This change ensures the wallet re-marks the tx's key images as
spent if the tx re-appears in the node's pool.
Without this commit:
1) read height from DB
2) add block to chain in separate thread
3) read chain for block id's and request them from peer
4) ERR in handle_response_chain_entry, peer's first block is the
one that was added to the chain, which has block idx=height from
step 1.
This commit reads the chain for height and highest block id's
in one go while holding the m_blockchain_lock to avoid the race.
Otherwise we can end up double counting txs towards the weight,
which can over-state the pool weight. E.g. relay tx to node in
stem phase, add its weight to pool weight, then receive tx
from another node, then bump the pool weight again. That double
counts the tx towards the pool weight.
If the weight exceeds the max, the node will "prune" txs from the
pool. Thus, over-counting is probably a cause of, but perhaps
not the only cause of:
https://github.com/seraphis-migration/monero/issues/148
