Added --rmdir flag to workspace remove

* tempest workspace remove --name command just remove the workspace
  entry from ~/.tempest/workspace.yaml and it does not deletes the
  workspace.

* by adding tempest workspace remove --name --rmdir removes
  the workspace as well as entry.

* renamed remove_workspace to remove_workspace_entry

Change-Id: I4528a23ca4933fdb7a3168f8dc99bbf0497ae5cc
3 files changed