Merge pull request #761 from edx/e0d/devstack-fix

conditionally creating dbs.

playbooks/roles/edxlocal/tasks/main.yml

@@ -20,6 +20,7 @@
     login_password={{ EDXAPP_MYSQL_PASSWORD }}
     state=present
     encoding=utf8
+  when: EDXAPP_MYSQL_USER
     
 - name: create a database for xqueue
   mysql_db: >
@@ -28,6 +29,7 @@
     login_password={{ XQUEUE_MYSQL_PASSWORD }}    
     state=present
     encoding=utf8
+  when: XQUEUE_MYSQL_USER    
 
 - name: create a database for ora
   mysql_db: >
@@ -36,6 +38,7 @@
     login_password={{ ORA_MYSQL_PASSWORD }}    
     state=present
     encoding=utf8
+  when: ORA_MYSQL_USER    
 
 - name: create a database for discern
   mysql_db: >
@@ -44,6 +47,7 @@
     login_password={{ DISCERN_MYSQL_PASSWORD }}    
     state=present
     encoding=utf8
+  when: DISCERN_MYSQL_USER    
 
 
 - name: install memcached