Since socket keepalive APIs for UDP encapsulation sockets are
public to generic app. In order to ensure the given fd is valid,
this change verifies the resource id inside the UDP
encapsulation socket by using methods provided by IpSecService.
Bug: 125517194
Fix: 123968920
Test: 1. atest FrameworksNetTests --generate-new-metrics 10
2. atestcom.android.server.ConnectivityServiceTest \
#testNattSocketKeepalives --generate-new-metrics 100
Change-Id: I408aacc19b364683854d15a095c34e72389a6e5b
2bb85a0bc0