Allow proxy plugins to have capabilities

Signed-off-by: Kern Walster <walster@amazon.com>

cmd/containerd/server/config/config.go

@@ -238,6 +238,7 @@ type ProxyPlugin struct {
 	Address      string            `toml:"address"`
 	Platform     string            `toml:"platform"`
 	Exports      map[string]string `toml:"exports"`
+	Capabilities []string          `toml:"capabilities"`
 }
 
 // Decode unmarshals a plugin specific configuration by plugin id

cmd/containerd/server/server.go

@@ -542,6 +542,7 @@ func LoadPlugins(ctx context.Context, config *srvconfig.Config) ([]plugin.Regist
 			InitFn: func(ic *plugin.InitContext) (interface{}, error) {
 				ic.Meta.Exports = exports
 				ic.Meta.Platforms = append(ic.Meta.Platforms, p)
+				ic.Meta.Capabilities = pp.Capabilities
 				conn, err := clients.getClient(address)
 				if err != nil {
 					return nil, err