[libvirt] [PATCH 0/2] Some new utility functions

I'm planning to use these to fix the problems with creating storage volumes on root-squashing NFS servers, but since they may be of general utility I thought I'd throw them out for comments beforehand - it something different would make them more generally useful, better to change it now than after I've already finished code to use them. My plan is to use virRunWithHook() to call setuid (or possibly some sort of capng calisthenics) prior to execing qemu-img and qcow-create. virFileCreate and virDirCreate will be used when creating raw volumes. I have written test code to verify that virFileCreate works in several different scenarios. Haven't done so with virRun yet, but it's a fairly simple change, just exposing __virExec arguments that were already there. (I'd previously written test code (yes, it worked ;-)) that used a virRun with uid/gid args added on, but have decided against that approach, since this seems more flexible)