Re: [Libguestfs] [PATCH v2] launch: Close file descriptors after fork (RHBZ#1123007).

This refactors existing code to close file descriptors in the recovery process, and also adds code to close file descriptors between the fork() and exec() of QEMU or User-Mode Linux. The reason is to avoid leaking main process file descriptors where the main process (or other libraries in the main process) are not setting O_CLOEXEC at all or not setting it atomically. Python is a particular culprit. See also this OpenStack Nova bug report: https://bugs.launchpad.net/nova/+bug/1313477 Thanks: Qin Zhao for identifying and characterizing the problem in Nova. This is version 2 of this commit. This commit is identical to the reverted commit 115fcc34325f965ac3723683e4462fc667dcd254 except that we don't close stderr.