Add missing include template in admin migrate host form
If migrate host action missing "ajax-modal", it will can not find
"_migrate_host.html"
Closes-bug:
{% load i18n %}
{% block title %}{% trans "Migrate Host" %}{% endblock %}
-{% block main %}{% endblock %}
+{% block main %}
+ {% include 'admin/hypervisors/compute/_migrate_host.html' %}
+{% endblock %}
