[IT4.1] Clean up to remove no-op logic

The design inside NMS allows the interface activity to be updated
from either radio itself or from other sources. However, it's
never used since it was introduced. In current code, the signal
never comes from radio. Part of the logic in
notifyInterfaceClassActivity is actually no operation performed.

Remove the no-op logic first to support the follow up migration
between CS and NMS for ConnectivityService mainline.

Bug: 170598012
Test: atest FrameworksNetTests
Change-Id: I4a1fc3a1e1045c3f4dd4ec30dad1ba88ce281b37