Prevent Closure of Underlying Socket FDs

The version of applyTransportModeTransform() and
removeTransportModeTransform() that accepted
Socket and DatagramSocket were closing the underlying
FDs upon return. It's unclear whether this is due to
a behavior change elsewhere in ParcelFileDescriptor,
but either way, converting to using getFileDescriptor$
and then calling dup() explicitly rather than relying
on ParcelFileDescriptor seems like a better idea anyway.

Bug: 72047396
Test: CTS - IpSecManagerTest.testCreateTransform()
Change-Id: Ia2f02564e1289f25bf113dbb861fcfd2240537a7