The Cast volume UI doesn't show up

-Call startScan() in SettingsLib and remove redundant api

Bug: 176774510
Test: atest MediaOutputAdapterTest MediaOutputControllerTest MediaOutputBaseDialogTest MediaOutputDialogTest MediaOutputGroupAdapterTest MediaOutputGroupDialogTest
Change-Id: I2a2f704f72f0eb056bb0d68fc10f34dbc117f07a
6 files changed