CI: Increase clone depth and do better cleanup

CI: Increase clone depth and do better cleanup

The original clone depth of 10 was causing the need to rebase
changes whose parent was older than the 10 commits.  The clone
depth has been increased to 100.

Workspace cleanup was only happening for successful builds which
wasn't enough to keep the 8G workspace in-memory drives on the
docker slaves from filling up.  Now the workspaces are cleaned up
after every build regardless of success/failure.  If you need to
preserve builds temporarily, you can log into Jenkins/Manage
Jenkins/Configure System and change the CLEANUP_WS_* environment
variable for the job type you're troubleshooting to "FALSE".

Change-Id: I0d7366e87cea714e5dbc9488caf718802fce75ca