Add 'manage_service_maintenance'. Don't manage services scheduling while upgrading.

For some special cases, don't manage services scheduling both enable and
disable before and after upgrade procedure.

Change-Id: I21ab967bc147c0404dae5b010b2009931307ceaf
Related-Prod: PROD-30156
diff --git a/README.rst b/README.rst
index 4fa35ec..7991408 100644
--- a/README.rst
+++ b/README.rst
@@ -176,6 +176,23 @@
         oslo_concurrency:
           lock_path: '/var/lock/manila'
 
+Don't manage services scheduling while upgrade
+----------------------------------------------
+For some special cases, don't manage services scheduling both enable and disable
+before and after upgrade procedure.
+
+If 'manage_service_maintenance: true' or not present - default behavior, disable services
+before upgrade and enable it after upgrade.
+If 'manage_service_maintenance: false' - don't disable and don't enable upgraded services
+scheduling before and after upgrade.
+
+.. code-block:: yaml
+
+    manila:
+      upgrade:
+        manage_service_maintenance: false
+
+
 More information
 ================