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/namespace_opts.go

@@ -0,0 +1,75 @@
+/*
+   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
+
+type NamespaceOpts func(s *Namespace) error
+
+// Capabilities
+func WithCapabilityPortMap(portMapping []PortMapping) NamespaceOpts {
+	return func(c *Namespace) error {
+		c.capabilityArgs["portMappings"] = portMapping
+		return nil
+	}
+}
+
+func WithCapabilityIPRanges(ipRanges []IPRanges) NamespaceOpts {
+	return func(c *Namespace) error {
+		c.capabilityArgs["ipRanges"] = ipRanges
+		return nil
+	}
+}
+
+// WithCapabilityBandWitdh adds support for traffic shaping:
+// https://github.com/heptio/cni-plugins/tree/master/plugins/meta/bandwidth
+func WithCapabilityBandWidth(bandWidth BandWidth) NamespaceOpts {
+	return func(c *Namespace) error {
+		c.capabilityArgs["bandwidth"] = bandWidth
+		return nil
+	}
+}
+
+// WithCapabilityDNS adds support for dns
+func WithCapabilityDNS(dns DNS) NamespaceOpts {
+	return func(c *Namespace) error {
+		c.capabilityArgs["dns"] = dns
+		return nil
+	}
+}
+
+func WithCapability(name string, capability interface{}) NamespaceOpts {
+	return func(c *Namespace) error {
+		c.capabilityArgs[name] = capability
+		return nil
+	}
+}
+
+// Args
+func WithLabels(labels map[string]string) NamespaceOpts {
+	return func(c *Namespace) error {
+		for k, v := range labels {
+			c.args[k] = v
+		}
+		return nil
+	}
+}
+
+func WithArgs(k, v string) NamespaceOpts {
+	return func(c *Namespace) error {
+		c.args[k] = v
+		return nil
+	}
+}