Get Multiple Instance Migration Status

<ul> <li>Retrieve the status of a previously initiated multiple instance migrations. <li>To initiate multiple instance migrations from AWS, use the `Import Multiple Instances From AWS` call. <li>Upon initiation, the migration will be in the state of `MIGRATE_START`. <li>Possible final states for each migration include `MIGRATE_CANCEL`, `MIGRATE_FINISH`, and `MIGRATE_ERROR`. <ul>