Dockerfile: Support multiple stage build in manager and cli

[gaocegege]

Same as #23

I am not sure if we should copy the CLI from the docker container. But I follow the convention to use centos instead of alpine to get the runnable binary from the container.

/assign @YujiOshima

[gaocegege]

PTAL @YujiOshima

[YujiOshima]

Why you use not golang:alpine but golang:1.8.2 ?

[gaocegege]

Because you can not build the binary in alpine and use it in ubuntu or centos.

https://stackoverflow.com/questions/36279253/go-compiled-binary-wont-run-in-an-alpine-docker-container-on-ubuntu-host?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

I tried to copy the binary build in alpine and call it in ubuntu it returns:

$ ls -l ./bin
-rwxr-xr-x 1 ist ist 12733320 4月  10 10:51 katib-cli
$ ./bin/katib-cli
zsh: no such file or directory: ./bin/katib-cli

Thus we have to build it in a normal go image. And I think we could avoid it by installing the binary from another way.

[YujiOshima]

Ah, OK. I understood. And I agree we should look for another way.
Anyway, LGTM for this PR.

[k8s-ci-robot]

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[YujiOshima]

/lgtm

[k8s-ci-robot]

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