Fix a bug in fetching the XML URL.
Fix a bug in fetching the XML URL.

In Discover, the reponse was lowercased for comparison.  However,
this caused a 404 - Not found when fetching the url provided by
the location header if the url contained uppercase.

ok @owainga

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