adb: win32: don't shutdown socket when closing.

This appears to be an attempt to do orderly shutdown, but it doesn't
wait until the socket becomes readable, so it doesn't actually work. We
implement orderly shutdown elsewhere already, so delete this so that we
don't accidentally shutdown a duped socket.

Test: wine adb_test
Change-Id: I35f8843e8e6dbc7886fd545f0e43375a005e160f