doc: add server status to concept.rst

some server status are missing, add them to the list.
also, remove a duplicate server status for creating server.

blueprint complete-todo-in-api-concept-doc

Change-Id: Ib25b57b5044df8dc8061a6de9978d9ee840885dd

api-guide/source/server_concepts.rst

@@ -30,8 +30,13 @@ server status is one of the following values:
    pulling the power plug on a physical server, plugging it back in, and
    rebooting it.
 
+-  ``MIGRATING``: The server is under migrating. This is caused by a
+   live migration (moving a server that is active) action.
+
 -  ``PASSWORD``: The password is being reset on the server.
 
+-  ``PAUSED``: The server is paused.
+
 -  ``REBOOT``: The server is in a soft reboot state. A reboot command
    was passed to the operating system.
 
@@ -46,6 +51,12 @@ server status is one of the following values:
    some reason. The destination server is being cleaned up and the
    original source server is restarting.
 
+-  ``SHELVED``: The server is in shelved state. Depends on the shelve offload
+   time, the server will be automatically shelved off loaded.
+
+-  ``SHELVED_OFFLOADED``: The shelved server is offloaded (removed from the
+   compute host) and it needs unshelved action to be used again.
+
 -  ``SHUTOFF``: The virtual machine (VM) was powered down by the user,
    but not through the OpenStack Compute API. For example, the user
    issued a ``shutdown -h`` command from within the server. If
@@ -55,6 +66,11 @@ server status is one of the following values:
    be deleted first, depending on the value in the
    *``shutdown_terminate``* database field on the Instance model.
 
+-  ``SOFT_DELETED``: The server is marked as deleted while will keep in the
+   cloud for some time(configurable), during the period authorized user can
+   restore the server back to normal state. When the time expires, the
+   server will be deleted permanently.
+
 -  ``SUSPENDED``: The server is suspended, either by request or
    necessity. This status appears for only the following hypervisors:
    XenServer/XCP, KVM, and ESXi. Administrative users may suspend a
@@ -87,8 +103,6 @@ Status Transition:
 
 ``ACTIVE``
 
-``BUILD``
-
 ``ERROR`` (on error)
 
 When you create a server, the operation asynchronously provisions a new