[Provider Model] Fix WiFi SSID disappear issue

- When WiFi is connected, there will be no internet access for a short
time. Need to detect the ConnectivityManager network to assign WiFi to
the default network, and make sure that the Wi-Fi connection is ready
for internet access.

- Refine the main thread functions to avoid calling unnecessary
functions

Bug: 195893061
Test: manual test
atest -c InternetAdapterTest \
         InternetDialogControllerTest \
         InternetDialogTest

Change-Id: I505c9b044f8b139fb6c5d4df415c5ad56ce7b301