Force creation of Socket upon Transform application

This change forces Socket and DatagramSocket to populate the
SocketImpl, ensuring that the socket file descriptor can be
retrieved when applying Transport mode Transforms

This is done by calling getSoLinger(), triggering a getImpl(), which
triggers setImpl() if needed.

Bug: 77491294
Test: Added tests in IpSecManagerTest, ran on walleye
Change-Id: I40da08b031357710eb794e0f866aec5660c79594