Rewrite lxcDomainAttachDeviceHostdevStorageLive 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 1754c7f0)

Conflicts:
	src/lxc/lxc_driver.c: OOM + cgroups error reporting