Remove unused ExecFifoPath

In container process's Init function, we use
fd + execFifoFilename to open exec fifo, so this
field in init config is never used.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

libcontainer/container_linux.go

@@ -450,7 +450,6 @@ func (c *linuxContainer) newInitConfig(process *Process) *initConfig {
 		AppArmorProfile:  c.config.AppArmorProfile,
 		ProcessLabel:     c.config.ProcessLabel,
 		Rlimits:          c.config.Rlimits,
-		ExecFifoPath:     filepath.Join(c.root, execFifoFilename),
 	}
 	if process.NoNewPrivileges != nil {
 		cfg.NoNewPrivileges = *process.NoNewPrivileges

libcontainer/init_linux.go

@@ -59,7 +59,6 @@ type initConfig struct {
 	PassedFilesCount int              `json:"passed_files_count"`
 	ContainerId      string           `json:"containerid"`
 	Rlimits          []configs.Rlimit `json:"rlimits"`
-	ExecFifoPath     string           `json:"start_pipe_path"`
 	CreateConsole    bool             `json:"create_console"`
 }