test: Fix mockContainer

Latest libcontainer vendoring update introduced a new function as part
of the Container Go interface, OCIState().
The mockContainer interface needs to implement this too, otherwise the
tests won't compile.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

mockcontainer.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/opencontainers/runc/libcontainer"
 	"github.com/opencontainers/runc/libcontainer/configs"
+	"github.com/opencontainers/runtime-spec/specs-go"
 )
 
 type mockContainer struct {
@@ -33,6 +34,10 @@ func (m *mockContainer) State() (*libcontainer.State, error) {
 	return nil, nil
 }
 
+func (m *mockContainer) OCIState() (*specs.State, error) {
+	return nil, nil
+}
+
 func (m *mockContainer) Config() configs.Config {
 	return configs.Config{
 		Capabilities: &configs.Capabilities{},