Drop the expired entries in NetworkEvents table regularly. am: 2fc47b291f am: 7841630ed8

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/3252336

Change-Id: I558bea6604d458e05f4037fa4a92396270c00d2e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>