Do not block removing clients if notification manager quit.
Do not block removing clients if notification manager quit.

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