Remove DatagramSocket calls from IpSecManagerTest

Because the DatagramSocket version of the API is being
hidden, this test is being converted to use the
FileDescriptor version of applyTransportModeTransform()
and removeTransportModeTransform()

Bug: 37446006
Test: compilation
Change-Id: Ida4977a6e7496ce6b4de38bfd48bd6a162cab874
1 file changed