Fixed race condition when network request removed

When data network enters disconnected state, a
network request might be removed without setting
the state back to unstatisfied. Fixed by removing
the incorrect logic in detachNetworkRequest. Also
rearranged the callback order to make sure all
network requests are detached before calling the
disconnected callback.

Test: atest DataNetworkControllerTest
Fix: 227280207

Change-Id: Ie69d8a49f8909988367565efa5a482481c8dc6b6