Previously, the caller can only know about the transport type of the underlying network. The information might not be enough if the device support WiFi STA+STA. Thus, provide an API for the caller to get the correct underlying network. Bug: 191918368 Test: atest FrameworksNetTests:NetworkCapabilitiesTest Change-Id: I7752b2356770f4572f6ca4cbaecaa45c09d6d72f