Add a handler thread check to all public methods am: d5b24b4855

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2593665

Change-Id: Iba5c8fe6f66d8df17c34d79c289ca4c799b555b3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>