Description of problem:
libvirt will not start an lxc container when the user namespace ID mapping feature is enabled. The same container starts successfully when the feature is disabled.

Version-Release number of selected component (if applicable):
libvirt-daemon-driver-lxc-1.1.3.5-2.fc20.x86_64
kernel-3.14.5-200.fc20.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Create a container filesystem:
# yum -y --releasever=20 --nogpg --installroot=/var/lib/libvirt/filesystems/mycontainer \
          --disablerepo='*' --enablerepo=fedora install \
          systemd passwd yum fedora-release vim-minimal openssh-server procps-ng
 # echo "pts/0" >> /var/lib/libvirt/filesystems/mycontainer/etc/securetty
 # chroot /var/lib/libvirt/filesystems/mycontainer /bin/passwd root

2. Create the container:
# virt-install --connect lxc:/// --name mycontainer --ram 256 \
              --filesystem /var/lib/libvirt/filesystems/mycontainer,/

3. Enable the idmap feature:
  <idmap>
    <uid start='0' target='1000' count='10'/>
    <gid start='0' target='1000' count='10'/>
  </idmap>

4. Start the container:
# virsh --connect lxc:/// start mycontainer

Actual results:
Error starting domain: internal error: guest failed to start: PATH=/bin:/sbin TERM=linux container=lxc-libvirt container_uuid=c134f57d-f4ff-4602-b7bb-c7370e83bc9f LIBVIRT_LXC_UUID=c134f57d-f4ff-4602-b7bb-c7370e83bc9f LIBVIRT_LXC_NAME=mycontainer /sbin/init
error receiving signal from container: Input/output error

Expected results:
Container should start normally, as when idmap configuration is not present.

Additional info:
/var/log/libvirt/lxc/mycontainer.log contains:

2014-06-08 01:05:49.397+0000: starting up
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin LIBVIRT_DEBUG=3 LIBVIRT_LOG_OUTPUTS=3:stderr /usr/libexec/libvirt_lxc --name mycontainer --console 22 --security=selinux --handshake 25 --background --veth veth1
PATH=/bin:/sbin TERM=linux container=lxc-libvirt container_uuid=c134f57d-f4ff-4602-b7bb-c7370e83bc9f LIBVIRT_LXC_UUID=c134f57d-f4ff-4602-b7bb-c7370e83bc9f LIBVIRT_LXC_NAME=mycontainer /sbin/init
2014-06-08 01:05:49.512+0000: 1: info : libvirt version: 1.1.3.5, package: 2.fc20 (Fedora Project, 2014-05-19-22:55:50, buildvm-04.phx2.fedoraproject.org)
2014-06-08 01:05:49.512+0000: 1: error : lxcContainerMountFSDev:959 : Failed to mount /.oldroot//run/libvirt/lxc/mycontainer.dev on /dev: Invalid argument
2014-06-08 01:05:49.512+0000: 1: error : lxcContainerMountFSDevPTS:986 : Cannot create /dev/pts: Permission denied
2014-06-08 01:05:49.512+0000: 1: error : lxcContainerSetupDevices:1023 : Failed to symlink device /dev/stdin to /proc/self/fd/0: Permission denied
2014-06-08 01:05:49.512+0000: 2303: info : libvirt version: 1.1.3.5, package: 2.fc20 (Fedora Project, 2014-05-19-22:55:50, buildvm-04.phx2.fedoraproject.org)
2014-06-08 01:05:49.512+0000: 2303: error : virLXCControllerRun:2188 : error receiving signal from container: Input/output error
error receiving signal from container: Input/output error
2014-06-08 01:05:49.533+0000: 2303: error : virCommandWait:2376 : internal error: Child process (ip link del veth1) unexpected exit status 1: Cannot find device "veth1"