[net processing] Inline and simplify UpdatePreferredDownload
[net processing] Inline and simplify UpdatePreferredDownload

We inline `UpdatePreferredDownload` because it is only used in one
location during the version handshake. We simplify it by removing the
initial subtraction of `state->fPreferredDownload` from
`nPreferredDownload`. This is ok since the version handshake is only
called once per peer and `state->fPreferredDownload` will always be
false before the newly inlined code is called, making the subtraction a
noop.

ajtowns/bitcoin,fujicoin/fujicoin,fujicoin/fujicoin,AkioNak/bitcoin,instagibbs/bitcoin,particl/particl-core,sstone/bitcoin,tecnovert/particl-core,domob1812/bitcoin,mruddy/bitcoin,jlopp/statoshi,sstone/bitcoin,mruddy/bitcoin,jamesob/bitcoin,jamesob/bitcoin,tecnovert/particl-core,jamesob/bitcoin,fanquake/bitcoin,bitcoin/bitcoin,anditto/bitcoin,ajtowns/bitcoin,bitcoinsSG/bitcoin,andreaskern/bitcoin,jamesob/bitcoin,instagibbs/bitcoin,bitcoin/bitcoin,sstone/bitcoin,anditto/bitcoin,ajtowns/bitcoin,AkioNak/bitcoin,Xekyo/bitcoin,jambolo/bitcoin,fanquake/bitcoin,particl/particl-core,fanquake/bitcoin,GroestlCoin/GroestlCoin,particl/particl-core,bitcoinsSG/bitcoin,sstone/bitcoin,instagibbs/bitcoin,GroestlCoin/bitcoin,fujicoin/fujicoin,namecoin/namecore,AkioNak/bitcoin,GroestlCoin/GroestlCoin,sstone/bitcoin,bitcoin/bitcoin,jambolo/bitcoin,Xekyo/bitcoin,kallewoof/bitcoin,lateminer/bitcoin,mruddy/bitcoin,namecoin/namecore,sstone/bitcoin,bitcoin/bitcoin,jlopp/statoshi,jambolo/bitcoin,kallewoof/bitcoin,GroestlCoin/bitcoin,domob1812/bitcoin,lateminer/bitcoin,jambolo/bitcoin,jlopp/statoshi,domob1812/bitcoin,particl/particl-core,sipsorcery/bitcoin,fujicoin/fujicoin,fujicoin/fujicoin,lateminer/bitcoin,sipsorcery/bitcoin,bitcoinsSG/bitcoin,kallewoof/bitcoin,kallewoof/bitcoin,anditto/bitcoin,jambolo/bitcoin,fanquake/bitcoin,bitcoinsSG/bitcoin,particl/particl-core,jlopp/statoshi,namecoin/namecoin-core,mruddy/bitcoin,anditto/bitcoin,fanquake/bitcoin,mruddy/bitcoin,andreaskern/bitcoin,AkioNak/bitcoin,tecnovert/particl-core,andreaskern/bitcoin,tecnovert/particl-core,instagibbs/bitcoin,anditto/bitcoin,GroestlCoin/GroestlCoin,fanquake/bitcoin,tecnovert/particl-core,namecoin/namecoin-core,jlopp/statoshi,Xekyo/bitcoin,jamesob/bitcoin,namecoin/namecoin-core,Xekyo/bitcoin,GroestlCoin/bitcoin,instagibbs/bitcoin,GroestlCoin/bitcoin,fujicoin/fujicoin,andreaskern/bitcoin,GroestlCoin/bitcoin,GroestlCoin/GroestlCoin,bitcoinsSG/bitcoin,namecoin/namecore,AkioNak/bitcoin,sipsorcery/bitcoin,GroestlCoin/GroestlCoin,tecnovert/particl-core,sipsorcery/bitcoin,namecoin/namecoin-core,andreaskern/bitcoin,bitcoinsSG/bitcoin,Xekyo/bitcoin,bitcoin/bitcoin,lateminer/bitcoin,jamesob/bitcoin,jambolo/bitcoin,ajtowns/bitcoin,lateminer/bitcoin,sipsorcery/bitcoin,mruddy/bitcoin,namecoin/namecore,domob1812/bitcoin,anditto/bitcoin,sipsorcery/bitcoin,ajtowns/bitcoin,domob1812/bitcoin,namecoin/namecoin-core,namecoin/namecore,domob1812/bitcoin,AkioNak/bitcoin,lateminer/bitcoin,particl/particl-core,namecoin/namecoin-core,instagibbs/bitcoin,andreaskern/bitcoin,GroestlCoin/GroestlCoin,bitcoin/bitcoin,kallewoof/bitcoin,jlopp/statoshi,GroestlCoin/bitcoin,Xekyo/bitcoin,kallewoof/bitcoin,namecoin/namecore,ajtowns/bitcoin