FIX Plugins must be removed after each "tagging"

docker.go

@@ -214,6 +214,10 @@ func (p Plugin) Exec() error {
 		if !p.Dryrun {
 			cmds = append(cmds, commandPush(p.Build, tag)) // docker push
 		}
+
+		if p.Build.IsPlugin {
+			cmds = append(cmds, exec.Command(dockerExe, "plugin", "rm", p.Build.Repo+":"+tag))
+		}
 	}
 
 	// execute all commands in batch mode.