Rewrite lxcDomainAttachDeviceDiskLive function to use the
virProcessRunInMountNamespace helper. This avoids risk of
a malicious guest replacing /dev with a absolute symlink,
tricking the driver into changing the host OS filesystem.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 4dd3a7d5)