peer: Use debug log for inability to start peer.
peer: Use debug log for inability to start peer.

The inability for a peer to negotiate is not something that should be a
warning which implies something is wrong.  On the contrary, it is quite
expected that various peers will connect (or be connected to) that are
unable to properly negotiate for a variety of reasons.  One example would
be a peer that is too old.

Also, while here take care of a few style nits.

ppcsuite/ppcd,jongillham/btcd,tb00/btcd,ltcsuite/ltcd,btcsuite/btcd,dajohi/btcd,aakselrod/btcd,Roasbeef/btcd,stevenroose/btcd,wallclockbuilder/btcd,wallclockbuilder/btcd,stevenroose/btcd,adiabat/btcd,tb00/btcd,cqswxj2013/btcd,ltcsuite/ltcd,dajohi/btcd,davecgh/btcd,ppcsuite/ppcd,jongillham/btcd,davecgh/btcd,aakselrod/btcd,adiabat/btcd,Stash-Crypto/btcd,Roasbeef/btcd,Stash-Crypto/btcd,dajohi/btcd,cqswxj2013/btcd,btcsuite/btcd