Replace hidden ParcelFileDescriptor constructor usage

If IOException happens while trying to start keepalives sockets,
an invalid fd will be constructed. It will fail with
ERROR_INVALID_SOCKET if the user later calls start(). Current
design to construct the invalid fd use the hidden
ParcelFileDescriptor constructor which will not work for the
incoming ConnectivityService mainline. Thus, replace it with
the other formal API.

Bug: 170598012
Test: atest FrameworksNetTests
Change-Id: I57fd7ec2281c5e8c75481200bbde723ecf96982a