[Provider Model] Fixed Internet Settings always showing "Loading"

- The Internet Settings will restart itself if it's launching in lock
screen

- The "Loading" might not be hidden if the activity restarts itself

- Move the postDelayed runnable from onViewCreated() to onStart() to
avoid loss

Bug: 204041345
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=NetworkProviderSettingsTest

Change-Id: I516f1105c74b6c8853a72e71c20d2197495cc0d6