[osx] Fix issue with updating the /etc/shells file
[osx] Fix issue with updating the /etc/shells file

Ref alrra/dotfiles#8
Fix alrra/dotfiles#8

newtonne/dotfiles,makabde/dotfiles,mickael83/ubuntu-dotfiles,zlot/dotfiles,christophermoura/dotfiles,christophermoura/dotfiles,b-boogaard/dotfiles,girishramnani/dotfiles,AlbertoElias/dotfiles,mickael83/ubuntu-dotfiles,wingy3181/dotfiles,EDiLD/dotfiles,pbrooks/dotfiles,sophatvathana/dotfiles,zlot/dotfiles,girishramnani/dotfiles,newtonne/dotfiles,wingy3181/dotfiles,wingy3181/dotfiles,oddlord/dotfiles,khornberg/dotfiles,makabde/dotfiles,AlbertoElias/dotfiles,EDiLD/dotfiles