Avoid unnecessary stopTethering when startTethering fails

- If Wi-Fi tethering is enabled or enabling, avoid to startTethering again.

- If Wi-Fi tethering is disabled or disabling, avoid to stopTethering again.

- Add more logs to know which module stopped Tethering.

Bug: 230457055
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=WifiTetherSwitchBarControllerTest

Change-Id: I51d42ac0117d935ecaa9fa7312acc646b43d3593