clatd: only wait 15s for SIGTERM during shutdown am: 9c05f75eaa am: 70da5b5a0a am: 2e34c79854

Original change: https://android-review.googlesource.com/c/platform/external/android-clat/+/2535679

Change-Id: I0d42457d27724b945f7a3b1dde636c0fdcc97bad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>