Update github.com/opencontainers/runtime-tools to v0.6.0

Also add new dependencies on github.com/xeipuuv/gojson* (brought up by
new runtime-tools) and adapt the containerd/cri code to replace the APIs
that were removed by runtime-tools.

In particular, add new helpers to handle the capabilities, since
runtime-tools now split them into separate sets of functions for each
capability set.

Replace g.Spec() with g.Config since g.Spec() has been deprecated in the
runtime-tools API.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>

vendor/github.com/opencontainers/runtime-tools/validate/validate_unsupported.go

@@ -0,0 +1,17 @@
+// +build !linux
+
+package validate
+
+import (
+	"github.com/syndtr/gocapability/capability"
+)
+
+// LastCap return last cap of system
+func LastCap() capability.Cap {
+	return capability.Cap(-1)
+}
+
+// CheckLinux is a noop on this platform
+func (v *Validator) CheckLinux() (errs error) {
+	return nil
+}