CDRIVER-880 must still call cursorid_prime()

We require the side effects of the function but ignore its return value.

Author: ksuarz

src/mongoc/mongoc-collection.c

@@ -307,6 +307,7 @@ mongoc_collection_aggregate (mongoc_collection_t       *collection, /* IN */
 
       /* we always return the cursor, even if it fails; users can detect the failure on performing
        * a cursor operation. see CDRIVER-880. */
+      _mongoc_cursor_cursorid_prime (cursor);
    } else {
       /* for older versions we get an array that we can create a synthetic
        * cursor on top of */