Show "seccomp" in docker info (#20909).

This pull request added a `SecurityOptions` field in the `GET /info`
output to show if there is `apparmor`, `seccomp`, or `selinux` suport.

The API changes are updated in the documentation and the update in
`GET /info` is covered by the test case in `TestInfoApi`.

This pull request fixes #20909.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
Upstream-commit: 190654aa2ee880c2052c0887a215b85d24049f6d
Component: engine

components/engine/docs/reference/api/docker_remote_api.md

@@ -117,6 +117,7 @@ This section lists each version from latest to oldest.  Each listing includes a
 [Docker Remote API v1.24](docker_remote_api_v1.24.md) documentation
 
 * `POST /containers/create` now takes `StorageOpt` field.
+* `GET /info` now returns `SecurityOptions` field, showing if `apparmor`, `seccomp`, or `selinux` is supported.
 
 ### v1.23 API changes
 

components/engine/docs/reference/api/docker_remote_api_v1.24.md

@@ -2239,6 +2239,11 @@ Display system-wide information
                 "127.0.0.0/8"
             ]
         },
+        "SecurityOptions": [
+            "apparmor",
+            "seccomp",
+            "selinux"
+        ],
         "ServerVersion": "1.9.0",
         "SwapLimit": false,
         "SystemStatus": [["State", "Healthy"]],