Merge #13439: rpc: Avoid "duplicate" return value for invalid submitblock

f74894480 Only set fNewBlock to true in AcceptBlock when we write to disk (Matt Corallo)
fa6e49731 rpc: Avoid "duplicate" return value for invalid submitblock (MarcoFalke)

Pull request description:

  This is #13395 with one more commit tacked on. MarcoFalke got tired of dealing with the stupidity of fixing a return code with too many rounds of review (not that I blame him). Honestly we should probably have no return whatsoever, but for now, this fixes it (as well as nLastBlockTime for eviction purposes).

  Original description:

  When `submitblock` of an invalid block, the return value should not be `"duplicate"`.

  This is only seen when the header was previously found (denoted by the incorrectly named boolean `fBlockPresent`). Fix this bug by removing `fBlockPresent`.

Tree-SHA512: 0ce3092655d5d904b4c8c5ff7479f73ce387144a738f20472b8af132564005c6db5594ae366e589508f6258506ee7a28b1c7995a83a8328b334f99316006bf2d

src/validation.cpp

@@ -3508,7 +3508,6 @@ bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CVali
         // request; don't process these.
         if (pindex->nChainWork < nMinimumChainWork) return true;
     }
-    if (fNewBlock) *fNewBlock = true;
 
     if (!CheckBlock(block, state, chainparams.GetConsensus()) ||
         !ContextualCheckBlock(block, state, chainparams.GetConsensus(), pindex->pprev)) {
@@ -3525,6 +3524,7 @@ bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CVali
         GetMainSignals().NewPoWValidBlock(pindex, pblock);
 
     // Write block to history file
+    if (fNewBlock) *fNewBlock = true;
     try {
         CDiskBlockPos blockPos = SaveBlockToDisk(block, pindex->nHeight, chainparams, dbp);
         if (blockPos.IsNull()) {