Add bin/update for course discovery.

playbooks/roles/edx_ansible/templates/update.j2

@@ -57,6 +57,7 @@ repos_to_cmd["edx-ora2"]="$edx_ansible_cmd ora2.yml -e 'ora2_version=$2'"
 repos_to_cmd["insights"]="$edx_ansible_cmd insights.yml -e 'INSIGHTS_VERSION=$2'"
 repos_to_cmd["ecommerce"]="$edx_ansible_cmd ecommerce.yml -e 'ECOMMERCE_VERSION=$2'"
 repos_to_cmd["programs"]="$edx_ansible_cmd programs.yml -e 'PROGRAMS_VERSION=$2'"
+repos_to_cmd["course_discovery"]="$edx_ansible_cmd course_discovery.yml -e 'COURSE_DISCOVERY_VERSION=$2'"
 
 
 if [[ -z $1 || -z $2 ]]; then