src/lxc/conf.c will explicitly mount it anyway.  Furthermore, the fstab
entry, which is getting processed first, did not specify -o newinstance.
This can cause the host's devpts entry mount options to change, as in
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/607636.
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>