Use defaults in config struct for btcctl.
Use defaults in config struct for btcctl.

Rather than doing a lot of if/else in the configuration load for btcctl,
set the default for the RPC server to localhost and the RPC cert to the
btcd cert, then override them as needed depending on the --wallet and
--testnet flags.

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