forkmknod: attach to mntns when task is chrooted
forkmknod: attach to mntns when task is chrooted

Have forkmknod first change cwd to the task's, then chroot to the task's root.
This relies on the fact that both symlinks are magic and that
chdir/chroot to them will reach the actual path the task's using.

Signed-off-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,mjeanson/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,Skarlso/lxd,stgraber/lxd,atxwebs/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,atxwebs/lxd,mjeanson/lxd,stgraber/lxd,lxc/lxd,mjeanson/lxd,Skarlso/lxd,hallyn/lxd,Skarlso/lxd,atxwebs/lxd,Skarlso/lxd,lxc/lxd,lxc/lxd,lxc/lxd