Fix pipe fds leak in copyInternalSpliceSocket

This method used a temporarily pipe to copy data but forget to close it
before exiting, which will cause fd leak. As the number of times this
method is called increases, the process may abort since the fd reaches
its limit. So close the pipe before exiting.

Bug: 344767008
Change-Id: I2028bf2e36e9dde9b6aaea1f7c758169e6842cc7