lxc: set nosuid+nodev+noexec flags on /proc/sys mount
lxc: set nosuid+nodev+noexec flags on /proc/sys mount

Future kernels will mandate the use of nosuid+nodev+noexec
flags when mounting the /proc/sys filesystem. Unconditionally
add them now since they don't harm things regardless and could
mitigate future security attacks.

libvirt/libvirt,VenkatDatta/libvirt,rlaager/libvirt,VenkatDatta/libvirt,eskultety/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,agx/libvirt,agx/libvirt,nertpinx/libvirt,datto/libvirt,zippy2/libvirt,libvirt/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt,taget/libvirt,andreabolognani/libvirt,agx/libvirt,zippy2/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,eskultety/libvirt,VenkatDatta/libvirt,zippy2/libvirt,jardasgit/libvirt,datto/libvirt,taget/libvirt,datto/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,andreabolognani/libvirt,rlaager/libvirt,datto/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,crobinso/libvirt,crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,andreabolognani/libvirt,taget/libvirt,taget/libvirt,jfehlig/libvirt,nertpinx/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,eskultety/libvirt,zippy2/libvirt,agx/libvirt,nertpinx/libvirt,eskultety/libvirt,jardasgit/libvirt,jfehlig/libvirt,taget/libvirt,olafhering/libvirt,olafhering/libvirt,VenkatDatta/libvirt,rlaager/libvirt,libvirt/libvirt,jardasgit/libvirt,rlaager/libvirt,jardasgit/libvirt,crobinso/libvirt,eskultety/libvirt,agx/libvirt,rlaager/libvirt,datto/libvirt