Correct version variable name.

playbooks/roles/xserver/tasks/deploy.yml

@@ -4,7 +4,7 @@
   - deploy
 
 - name: checkout code
-  git: dest={{ xserver_code_dir }} repo={{ xserver_source_repo }} version={{ lms_version }}
+  git: dest={{ xserver_code_dir }} repo={{ xserver_source_repo }} version={{ xserver_version }}
   tags:
   - deploy
 

playbooks/roles/xserver/vars/main.yml

@@ -4,4 +4,4 @@ xserver_code_dir: "{{ app_base_dir }}/xserver"
 xserver_source_repo: git://github.com/edx/xserver.git
 # This should probably be overridden in the playbook or groupvars
 # with the default pointing to the head of master.
-lms_version: HEAD
+xserver_version: HEAD