quiet_system: don't print cmd even when verbose mode
quiet_system: don't print cmd even when verbose mode

It's kinda annoying that quiet_system wasn't really quiet. This commit
fixes that.

mahori/brew,JCount/brew,DomT4/brew,staticfloat/brew,konqui/brew,JCount/brew,gordonmcshane/homebrew,reelsense/brew,sjackman/homebrew,maxim-belkin/brew,reitermarkus/brew,muellermartin/dist,Homebrew/brew,Linuxbrew/brew,claui/brew,ilovezfs/brew,gregory-nisbet/brew,vitorgalvao/brew,Homebrew/brew,Homebrew/brew,MikeMcQuaid/brew,konqui/brew,jmsundar/brew,ilovezfs/brew,JCount/brew,amar-laksh/brew_sudo,Linuxbrew/brew,konqui/brew,amar-laksh/brew_sudo,Homebrew/brew,zmwangx/brew,toonetown/homebrew,hanxue/linuxbrew,hanxue/linuxbrew,EricFromCanada/brew,zmwangx/brew,claui/brew,gregory-nisbet/brew,AnastasiaSulyagina/brew,nandub/brew,alyssais/brew,toonetown/homebrew,palxex/brew,claui/brew,pseudocody/brew,nandub/brew,maxim-belkin/brew,reitermarkus/brew,mgrimes/brew,DomT4/brew,staticfloat/brew,reelsense/brew,reelsense/brew,tonyg/homebrew,aw1621107/brew,toonetown/homebrew,mgrimes/brew,staticfloat/brew,EricFromCanada/brew,alyssais/brew,mgrimes/brew,Linuxbrew/brew,vitorgalvao/brew,MikeMcQuaid/brew,vitorgalvao/brew,EricFromCanada/brew,zmwangx/brew,rwhogg/brew,bfontaine/brew,pseudocody/brew,nandub/brew,vitorgalvao/brew,nandub/brew,rwhogg/brew,palxex/brew,mahori/brew,hanxue/linuxbrew,AnastasiaSulyagina/brew,sjackman/homebrew,mahori/brew,konqui/brew,mistydemeo/homebrew,jmsundar/brew,Linuxbrew/brew,bfontaine/brew,palxex/brew,aw1621107/brew,muellermartin/dist,muellermartin/dist,alyssais/brew,EricFromCanada/brew,DomT4/brew,maxim-belkin/brew,sjackman/homebrew,AnastasiaSulyagina/brew,reitermarkus/brew,amar-laksh/brew_sudo,claui/brew,mistydemeo/homebrew,ilovezfs/brew,tonyg/homebrew,aw1621107/brew,jmsundar/brew,sjackman/homebrew,JCount/brew,MikeMcQuaid/brew,bfontaine/brew,MikeMcQuaid/brew,tonyg/homebrew,rwhogg/brew,gordonmcshane/homebrew,mahori/brew,DomT4/brew,mistydemeo/homebrew,gordonmcshane/homebrew,pseudocody/brew,gregory-nisbet/brew,reitermarkus/brew