Refactor SocketNetlinkMonitor to make it buildable with system sdk am: 6e12ac60b8

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2524596

Change-Id: I04c27b11083e4adfa6a993ebc4ef81079d4019ad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>