[M86-LTS] camera: Explicitly exit during cros-camera pre-start

As a best practice, we should explicitly call exit during pre-start so
that no subsequent commands would have any effect.

BUG=b:191260938
TEST=restart cros-camera several times and verify camera is still
accessible

Change-Id: I8b2f1c74a974b5b308ac10cbedc57224ca0a7e5d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2967861
Tested-by: Jasmine Chen <lnishan@google.com>
Auto-Submit: Jasmine Chen <lnishan@google.com>
Reviewed-by: Shik Chen <shik@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
(cherry picked from commit 3e52465303b1fb4652a0e70126c60d9d42398501)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2971549
Reviewed-by: Jasmine Chen <lnishan@google.com>
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
Tested-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
(cherry picked from commit da126e230e5a14f4b9a51e2d6c43ddaa4423378d)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2992163
Reviewed-by: Artem Sumaneev <asumaneev@google.com>
Commit-Queue: Achuith Bhandarkar <achuith@chromium.org>
Tested-by: Achuith Bhandarkar <achuith@chromium.org>
diff --git a/camera/hal_adapter/init/cros-camera.conf b/camera/hal_adapter/init/cros-camera.conf
index ea148b5..129e468 100644
--- a/camera/hal_adapter/init/cros-camera.conf
+++ b/camera/hal_adapter/init/cros-camera.conf
@@ -44,6 +44,9 @@
   if [ "$(cros_config /camera clock)" = "boottime" ]; then
     printf "boottime" > "${UVC_CLOCK_FILE}" || true
   fi
+
+  # Exit here so that additional commands cannot be executed.
+  exit 0
 end script
 
 post-start script