Add 'all_tenants' for GET sec group api ref

GET /os-security-groups API accept 'all_tenants' [1]
as one of the query param to list all tenants sec groups.
But that is missing in api-ref [2]

..1
e9104dbaef/nova/network/security_group/neutron_driver.py (L178)
e9104dbaef/nova/compute/api.py (L5096)

..2 https://developer.openstack.org/api-ref/compute/#list-security-groups

Closes-Bug: #1734406

Change-Id: I2946f05716c9030f7880ac423cc64b49c04b2992

api-ref/source/os-security-groups.inc

@@ -35,6 +35,7 @@ Request
 
   - limit: limit_simple
   - offset: offset_simple
+  - all_tenants: all_tenants_sec_grp_query
 
 Response
 --------

api-ref/source/parameters.yaml

@@ -385,6 +385,15 @@ all_tenants_query:
   in: query
   required: false
   type: integer
+all_tenants_sec_grp_query:
+  description: |
+    Specify the ``all_tenants`` query parameter to list all security
+    groups for all projects. This is only allowed for admin users.
+    Value of this query parameter is not checked, only presence
+    is considered as request for all tenants.
+  in: query
+  required: false
+  type: string
 availability_zone_query_server:
   description: |
     Filter the server list result by server availability zone.