nri: add experimental NRI plugin.

Add a common NRI 'service' plugin. It takes care of relaying
requests and respones to and from NRI (external NRI plugins)
and the high-level containerd namespace-independent logic of
applying NRI container adjustments and updates to actual CRI
and other containers.

The namespace-dependent details of the necessary container
manipulation operations are to be implemented by namespace-
specific adaptations. This NRI plugin defines the API which
such adaptations need to implement.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

vendor/github.com/opencontainers/runtime-tools/validate/capabilities/validate_linux.go

@@ -0,0 +1,16 @@
+package capabilities
+
+import (
+	"github.com/syndtr/gocapability/capability"
+)
+
+// LastCap return last cap of system
+func LastCap() capability.Cap {
+	last := capability.CAP_LAST_CAP
+	// hack for RHEL6 which has no /proc/sys/kernel/cap_last_cap
+	if last == capability.Cap(63) {
+		last = capability.CAP_BLOCK_SUSPEND
+	}
+
+	return last
+}