validation: call RecalculateBestHeader in InvalidChainFound

This means that it is being called in two situations:
1.) As part of the invalidateblock rpc
2.) When we receive a block for which we have a valid
header in our block index, but the block turns out to be invalid

Author: mzumsande

src/validation.cpp

@@ -2046,7 +2046,7 @@ void Chainstate::InvalidChainFound(CBlockIndex* pindexNew)
         m_chainman.m_best_invalid = pindexNew;
     }
     if (m_chainman.m_best_header != nullptr && m_chainman.m_best_header->GetAncestor(pindexNew->nHeight) == pindexNew) {
-        m_chainman.m_best_header = m_chain.Tip();
+        m_chainman.RecalculateBestHeader();
     }
 
     LogPrintf("%s: invalid block=%s  height=%d  log2_work=%f  date=%s\n", __func__,

test/functional/rpc_invalidateblock.py

@@ -41,6 +41,8 @@ def run_test(self):
         self.nodes[0].invalidateblock(badhash)
         assert_equal(self.nodes[0].getblockcount(), 4)
         assert_equal(self.nodes[0].getbestblockhash(), besthash_n0)
+        # Should report consistent blockchain info
+        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"])
 
         self.log.info("Make sure we won't reorg to a lower work chain:")
         self.connect_nodes(1, 2)