Fix root mysql password setting

roles/dbserver/tasks/mysql.yml

@@ -25,7 +25,7 @@
 
 - name: Change MySQL or MariaDB root default password
   raw: if ! echo "SELECT VERSION();" | mysql -u root --password='{{ mysql_root_password }}' >/dev/null 2>&1 ; then echo "UPDATE mysql.user SET Password=PASSWORD('{{ mysql_root_password }}') WHERE User IN ('', 'root'); FLUSH PRIVILEGES;" | mysql --defaults-file=/etc/mysql/debian.cnf ; fi
-  when: mysql_root_password
+  when: mysql_root_password != ''
 
 - name: Ensure MySQL or MariaDB is running
   service: name=mysql state=started