Added direct HTTP deploy support

  The following new parameters were added to ironic.conf:
    - image_download_source: allowed values are swift,http.
      defaults to "swift"
    - http_image_subdir: The name of subdirectory under
      ronic-conductor node's HTTP root path. Defaults to
      "agent_images"

Related-Prod: PROD-32758
Change-Id: I468bcdb7b922292adf9e536339b857ab9c4ee4a4
diff --git a/README.rst b/README.rst
index ddf253f..e208f7b 100644
--- a/README.rst
+++ b/README.rst
@@ -259,6 +259,15 @@
           efi_system_partition_size: 200
           bios_boot_partition_size: 1
 
+Enable direct http deploy feature
+========================================================
+
+.. code-block:: yaml
+
+  ironic:
+    conductor:
+      image_download_source: http
+
 Upgrades
 ========