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: Id0c2c2fed0ae27912e8490d82ba9dc30819adc06
Related-Prod: PROD-30156
diff --git a/README.rst b/README.rst
index 44ee5f1..9abb02c 100644
--- a/README.rst
+++ b/README.rst
@@ -1029,3 +1029,20 @@
 |                               | operations, verify do not have dead network          |
 |                               | agents/compute services)                             |
 +-------------------------------+------------------------------------------------------+
+
+
+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
+
+    cinder:
+      upgrade:
+        manage_service_maintenance: false