[bug] pouch create should check the valid of image

[Letty5411]

Issue Description
When create a container using "pouch create", it should check if the image specified existed.
If not, an error is expected.

Describe what happened:

Describe what you expected to happen:

How to reproduce it (as minimally and precisely as possible):
#./pouch images
IMAGE ID IMAGE NAME SIZE
68effe31a4ae reg.docker.alibaba-inc.com/base/busybox:latest 527

#./pouch create busybox
INFO[2017-11-14 18:08:00.750619593] Calling POST /containers/create, client @
container's id: c73f484d33055bad722a3628817d51640991bf3b91de9920481ae8bbb8cc4775, name: c73f48

[root@10.218.145.76 /home/sit/letty/src/github.com/alibaba/pouch]
#ls /etc/pouchd/containers/
18f5fcef8ab38c620cb1b580207e2815f9d7699a6b0421986b80b009d60fcd74 d107b968b8fcba81950f82f999aa4f1ead4d86727a95077f69a4f73879a373d9
c73f484d33055bad722a3628817d51640991bf3b91de9920481ae8bbb8cc4775

[root@10.218.145.76 /home/sit/letty/src/github.com/alibaba/pouch]
#./pouch start c73f48
INFO[2017-11-14 18:08:16.371527369] Calling POST /containers/c73f48/start, client @
INFO[2017-11-14 18:08:16.371961585] start to subscribe io, backend: raw-file, id: c73f484d33055bad722a3628817d51640991bf3b91de9920481ae8bbb8cc4775
INFO[2017-11-14 18:08:16.372999071] close containerio backend: raw-file, id: c73f484d33055bad722a3628817d51640991bf3b91de9920481ae8bbb8cc4775
INFO[2017-11-14 18:08:16.373029703] close containerio backend: raw-file, id: c73f484d33055bad722a3628817d51640991bf3b91de9920481ae8bbb8cc4775
INFO[2017-11-14 18:08:16.373099901] finished to subscribe io, backend: raw-file, id: c73f484d33055bad722a3628817d51640991bf3b91de9920481ae8bbb8cc4775
ERRO[2017-11-14 18:08:16.412932700] invoke /containers/c73f48/start error Image not found. client @
failed to start container c73f48: Image not found

Anything else we need to know?:

Environment:

• pouch version (use pouch version):
• OS (e.g. from /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Others:

[allencloud]

+1

[Letty5411]

Close it as it has been fixed.