Revert "Allow form builders to trigger rebuilds."

This reverts commit 7a0efc1230.
... Rebuilding is/was kinda broken.

includes/ingest.form.inc

@@ -32,21 +32,7 @@
  */
 function islandora_ingest_form(array $form, array &$form_state, array $configuration) {
   islandora_ingest_form_init_form_state($form_state, $configuration);
-
-  $original_form = $form;
-  $form = islandora_ingest_form_execute_step($original_form, $form_state);
-
-  // XXX: One would think that this would be handled by Drupal proper; however,
-  //   it is not.  To trigger rebuilds from inside of a form building function
-  //   does not look to be provided for.
-  while ($form_state['rebuild'] === TRUE) {
-    $form_state['rebuild'] = FALSE;
-    // Might've changed the step...  Might need to include new files.
-    islandora_ingest_form_step_form_load_include($form_state);
-    $form = islandora_ingest_form_execute_step($original_form, $form_state);
-  }
-
-  return $form;
+  return islandora_ingest_form_execute_step($form, $form_state);
 }
 
 /**