Add migration capability to the script.

util/jenkins/ansible-deploy.sh

@@ -50,6 +50,8 @@ ease_version: $ease_version
 ansible_ssh_private_key_file: /var/lib/jenkins/${keypair}.pem
 PYPI_MIRROR_URL: 'https://pypi.edx.org/root/pypi/+simple/'
 GIT_MIRROR: 'git.edx.org'
+
+migrate_only: $run_migration
 EOF
 
 cat $extra_vars