qemuProcessBuildDestroyHugepagesPath: Don't warn on destroying non-existent path
    
    This function is called unconditionally from qemuProcessStop to
    make sure we leave no dangling dirs behind. However, whenever the
    directory we want to rmdir() is not there (e.g. because it hasn't
    been created in the first place because domain doesn't use
    hugepages at all), we produce a warning like this:
    
    2017-06-20 15:58:23.615+0000: 32638: warning :
    qemuProcessBuildDestroyHugepagesPath:3363 : Unable to remove
    hugepage path: /dev/hugepages/libvirt/qemu/1-instance-00000001
    (errno=2)
    
    Fix this by not producing the warning on ENOENT.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
    Reviewed-by: Martin Kletzander <mkletzan@redhat.com>