Do not restore accpet_ra if the default IPv6 route has lost. am: 97a0eece0a am: f650aec55b am: 81beaa1ea8 am: 08b5b7567e

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/2045177

Change-Id: I2ba5887583dbc9db80f18f75da268c08ed938382
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>