Merge "EthernetTetheringTest: join handler thread after calling quitSafely" am: 78fd43ec67

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2485639

Change-Id: Icb5c8b9571b47439fab93f4d880703aa001ad891
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>