Use exported field with struct tag in tests.
Use exported field with struct tag in tests.

Found by golint.

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