Fix socket descriptor leak from Zygote to child app

Due to an API change in LocalSocket, Zygote must now
manually close the FileDescriptor it created when it
registered a LocalServerSocket.  The LocalSocket.close()
routine will no longer do so.
Bug: 12114500
(cherry picked from commit 70ef29b04ee4ef7d7acfec79041dbe800961195e)

Change-Id: Ief23a3c99e007dc4aa6f94dfb47a1b2b6c854dad