Show progress bar when Wi-Fi scanning (QS)

Show the progress bar in Internet Dialog while we're currently
scanning for networks, and then stop when we receive the results of the
scan.

Fix: 308567866
Flag: NONE
Test: unit test
atest -c SystemUITests:AccessPointControllerImplTest \
         SystemUITests:InternetDialogTest \
         SystemUITests:InternetDialogControllerTest

Change-Id: I2205f7ea8c88f5fdc55c92430049b227a86f1ad5