threadnetwork: Avoid execute command if service does not exist am: 0afad08e...

threadnetwork: Avoid execute command if service does not exist am: 0afad08e am: bac748d1 am: 1d365aaf

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/3343649



Change-Id: Ia38ac205ad6086dffda75496230de3baf2866a51
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>