lxc: bump to version 2.1.1

Remove 0001-conf-fix-build-without-libcap.patch (already in 2.1.1)
Add 0001-Fix-compilation-on-toolchain-without-prlimit.patch (merged
upstream)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>