blockchain: mark blocks as invalid if they fail connectBlock
blockchain: mark blocks as invalid if they fail connectBlock

dajohi/btcd,wallclockbuilder/btcd,tb00/btcd,tb00/btcd,ppcsuite/ppcd,ppcsuite/ppcd,ltcsuite/ltcd,btcsuite/btcd,ltcsuite/ltcd,davecgh/btcd,dajohi/btcd,davecgh/btcd,wallclockbuilder/btcd,dajohi/btcd,btcsuite/btcd