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>

pkg/server/container_update_resources.go

@@ -157,5 +157,5 @@ func updateOCILinuxResource(spec *runtimespec.Spec, new *runtime.LinuxContainerR
 		g.SetLinuxResourcesCPUMems(new.GetCpusetMems())
 	}
 
-	return g.Spec(), nil
+	return g.Config, nil
 }