Improve logging of rejected blocks.
Improve logging of rejected blocks.

Rather than showing all errors from ProcessBlock as a failure, check if
the error is a RuleError meaning the block was rejected as opposed to
something actually going wrong and log it accordingly.

cjepson/btcd,1d4Nf6/btcd,btcsuitereleases/btcd,glv2/ppcd,DanielKrawisz/btcd,FactomProject/btcd,jrick/btcd,sysbot/btcd,ltcsuite/ltcd,ppcsuite/ppcd-old,Dirbaio/btcd,jrick/btcd,1d4Nf6/btcd,glv2/ppcd,btcsuitereleases/btcd,toddfries/btcd,pkothbauer/btcd,decred/dcrd,decred/dcrd,ppcsuite/ppcd-old,jimmysong/btcd,jcmincke/dcrd,jrick/dcrd,cqswxj2013/btcd,jongillham/btcd,mathiasrw/btcd,runeaune/btcd,FactomProject/btcd,CryptocurrencyCabal/htcd,adiabat/btcd,davecgh/btcd,tb00/btcd,btcsuite/btcd,jimmysong/btcd,Stash-Crypto/btcd,wallclockbuilder/btcd,cqswxj2013/btcd,mathiasrw/btcd,dan-da/btcd,cjepson/btcd,soapboxsys/ombfullnode,BitGo/prova,DanielKrawisz/btcd,hectorj/btcd,Stash-Crypto/btcd,jcmincke/dcrd,jcmincke/dcrd,Evil-Coin/Evil,adiabat/btcd,tb00/btcd,jrick/btcd,sysbot/btcd,dajohi/btcd,wallclockbuilder/btcd,danoctavian/btcd,dan-da/btcd,stevenroose/btcd,aakselrod/btcd,BitGo/prova,jongillham/btcd,btcsuite/btcd,qchain/btcd,Evil-Coin/Evil,runeaune/btcd,jrick/dcrd,dajohi/btcd,Roasbeef/btcd,CryptocurrencyCabal/htcd,Dirbaio/btcd,dajohi/btcd,Roasbeef/btcd,qchain/btcd,Cleawing/btcd,ppcsuite/ppcd,ppcsuite/ppcd,stevenroose/btcd,hectorj/btcd,pkothbauer/btcd,Cleawing/btcd,Dirbaio/btcd,soapboxsys/ombfullnode,davecgh/btcd,ltcsuite/ltcd,toddfries/btcd,danoctavian/btcd,aakselrod/btcd