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

test/functional/rpc_invalidateblock.py

@@ -41,6 +41,8 @@ class InvalidateTest(BitcoinTestFramework):
         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)