update runc to 2b18fe1d885ee5083ef9f0838fee39b62d653e30

This includes an improved fix for CVE-2019-5736 to reduce the
increased memory-consumption introduced by the original patch,
RHEL 7.6 getting into a loop due to a kernel bug in those kernels,
and improve compatibility with older kernels.

changes included:

- opencontainers/runc#1973 Vendor opencontainers/runtime-spec 29686dbc
- opencontainers/runc#1978 Remove detection for scope properties, which have always been broken
- opencontainers/runc#1963 Vendor in go-criu and use it for CRIU's RPC definition
- opencontainers/runc#1995 exec: expose --preserve-fds
- opencontainers/runc#2000 fix preserve-fds flag may cause runc hang
- opencontainers/runc#1968 Create bind mount mountpoints during restore
- opencontainers/runc#1984 nsenter: cloned_binary: "memfd" cleanups

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/opencontainers/runc/vendor.conf

@@ -1,8 +1,9 @@
 # OCI runtime-spec. When updating this, make sure you use a version tag rather
 # than a commit ID so it's much more obvious what version of the spec we are
 # using.
-github.com/opencontainers/runtime-spec 5684b8af48c1ac3b1451fa499724e30e3c20a294
+github.com/opencontainers/runtime-spec 29686dbc5559d93fb1ef402eeda3e35c38d75af4
 # Core libcontainer functionality.
+github.com/checkpoint-restore/go-criu v3.11
 github.com/mrunalp/fileutils ed869b029674c0e9ce4c0dfa781405c2d9946d08
 github.com/opencontainers/selinux v1.0.0-rc1
 github.com/seccomp/libseccomp-golang 84e90a91acea0f4e51e62bc1a75de18b1fc0790f