Port networking to CNI

Replaced netns utility with CNI plugins to create a bridge network
and allow communication between containers with firewall plugin.

Overwrite the CNI config in case it exists. Allow updating the config
on new versions.

Signed-off-by: Carlos de Paula <me@carlosedp.com>

vendor/github.com/containerd/go-cni/errors.go

@@ -0,0 +1,55 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package cni
+
+import (
+	"github.com/pkg/errors"
+)
+
+var (
+	ErrCNINotInitialized = errors.New("cni plugin not initialized")
+	ErrInvalidConfig     = errors.New("invalid cni config")
+	ErrNotFound          = errors.New("not found")
+	ErrRead              = errors.New("failed to read config file")
+	ErrInvalidResult     = errors.New("invalid result")
+	ErrLoad              = errors.New("failed to load cni config")
+)
+
+// IsCNINotInitialized returns true if the error is due to cni config not being initialized
+func IsCNINotInitialized(err error) bool {
+	return errors.Cause(err) == ErrCNINotInitialized
+}
+
+// IsInvalidConfig returns true if the error is invalid cni config
+func IsInvalidConfig(err error) bool {
+	return errors.Cause(err) == ErrInvalidConfig
+}
+
+// IsNotFound returns true if the error is due to a missing config or result
+func IsNotFound(err error) bool {
+	return errors.Cause(err) == ErrNotFound
+}
+
+// IsReadFailure return true if the error is a config read failure
+func IsReadFailure(err error) bool {
+	return errors.Cause(err) == ErrRead
+}
+
+// IsInvalidResult return true if the error is due to invalid cni result
+func IsInvalidResult(err error) bool {
+	return errors.Cause(err) == ErrInvalidResult
+}