add apex_available for networkstack_client am: d95b328a95 am: 7f9a4ac257

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1587575

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I4b352d36a2f3f8b598db18cb79f4b13d2ca00af3