Validate client permission for HeadlessSystemUser.

If device is running in  HSUM mode, if User 0 tries to access the
camera, validate that the client has the permission
android.permission.CAMERA_HEADLESS_SYSTEM_USER.

Bug:296959023
Test: Test that headless system user is not able to access
the camera without the new permission.

Change-Id: Ibc2ef43837d2e8739872697245e466d69f56f335
diff --git a/camera/camera_platform.aconfig b/camera/camera_platform.aconfig
index fc11518..6200489 100644
--- a/camera/camera_platform.aconfig
+++ b/camera/camera_platform.aconfig
@@ -6,3 +6,11 @@
      description: "Flag infrastructure test flag"
      bug: "292631208"
 }
+
+flag {
+     namespace: "camera_platform"
+     name: "camera_hsum_permission"
+     description: "Camera access by headless system user"
+     bug: "273539631"
+}
+