fix(shellcheck): fix shellcheck error

dev/setup-salt.sh

@@ -2,7 +2,7 @@
 
 # use the latest stable Salt from repo.saltstack.com
 wget -O - https://repo.saltstack.com/apt/ubuntu/14.04/amd64/latest/SALTSTACK-GPG-KEY.pub | sudo apt-key add -
-sudo echo 'deb http://repo.saltstack.com/apt/ubuntu/14.04/amd64/latest trusty main' > /etc/apt/sources.list.d/saltstack.list
+echo 'deb http://repo.saltstack.com/apt/ubuntu/14.04/amd64/latest trusty main' | sudo tee /etc/apt/sources.list.d/saltstack.list
 
 sudo apt-get update -y
 sudo apt-get install salt-master -y