fix panic when adding new container and process after sandbox is closed
fix panic when adding new container and process after sandbox is closed

Fixes panic:
panic(0x11a1ce0, 0xc4218baa70)
        /usr/local/go/src/runtime/panic.go:458 +0x243
github.com/hyperhq/hyperd/vendor/github.com/hyperhq/runv/hyperstart/libhyperstart.(*serialBasedHyperstart).setupProcessIo(0xc421024af0, 0xc42118f6c0, 0xc420655100)
        /home/jenkins/workspace/gopath/src/github.com/hyperhq/hyperd/vendor/github.com/hyperhq/runv/hyperstart/libhyperstart/serial.go:602 +0x19c
github.com/hyperhq/hyperd/vendor/github.com/hyperhq/runv/hyperstart/libhyperstart.(*serialBasedHyperstart).AddProcess(0xc421024af0, 0xc4212a8340, 0x40, 0xc4215cec00, 0x3, 0xc4200add80, 0x2, 0x4, 0xc420648000, 0x7f0dfae2e000, ...)
        /home/jenkins/workspace/gopath/src/github.com/hyperhq/hyperd/vendor/github.com/hyperhq/runv/hyperstart/libhyperstart/serial.go:655 +0x250
github.com/hyperhq/hyperd/vendor/github.com/hyperhq/runv/hypervisor.(*Vm).AddProcess(0xc4206bfb00, 0xc4212a8340, 0x40, 0xc4218ba830, 0xf, 0xc42118f600, 0xc42118f500, 0x2, 0x4, 0xc42118f640, ...)

Signed-off-by: Peng Tao <39d8af57313740070ea49547576f55682fe5221a@gmail.com>

gao-feng/runv,hyperhq/runv,bergwolf/runv,jinfenw/runv,feiskyer/runv,hyperhq/runv,bergwolf/runv,laijs/runv,gnawux/runv,gnawux/runv,feiskyer/runv,hyperhq/runv,gao-feng/runv,jinfenw/runv,gao-feng/runv,jinfenw/runv,laijs/runv,gnawux/runv,laijs/runv,bergwolf/runv