Don't cd to /tmp in environment-setup.sh

This script is used by developers to activate the kayobe virtual
environment and source the configuration's kayobe-env file. A cd to /tmp
is an unexpected outcome of running the script.

To test the location-independent installation, remove the chdir from the
zuul job tasks that execute kayobe commands.

Change-Id: I59194952901fa648382489f48dc7aafb03d3a682
Story: 2004252
Task: 29347