Create base image for admission service

[TommyLike]

Now we would build admission service image from ground in our CI workflow, this patch creates a base image which consists of the installation of required libraries for admission service. This can improve the performance when testing.

For #282

image name: volcanosh/vk-admission-base

image content:

Sending build context to Docker daemon  9.216kB
Step 1/4 : FROM alpine:latest
 ---> 055936d39205
Step 2/4 : ARG KUBE_VERSION="1.13.1"
 ---> Running in 9a9a54338322
Removing intermediate container 9a9a54338322
 ---> 8e7e7a086e00
Step 3/4 : RUN apk add --update ca-certificates &&     apk add --update openssl &&     apk add --update -t deps curl &&     curl -L https://storage.googleapis.com/kubernetes-release/release/v$KUBE_VERSION/bin/linux/amd64/kubectl -o /usr/local/bin/kubectl &&     chmod +x /usr/local/bin/kubectl &&     apk del --purge deps &&     rm /var/cache/apk/*
 ---> Running in 00a41be6c337
fetch http://dl-cdn.alpinelinux.org/alpine/v3.9/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.9/community/x86_64/APKINDEX.tar.gz
(1/1) Installing ca-certificates (20190108-r0)
Executing busybox-1.29.3-r10.trigger
Executing ca-certificates-20190108-r0.trigger
OK: 6 MiB in 15 packages
(1/1) Installing openssl (1.1.1b-r1)
Executing busybox-1.29.3-r10.trigger
OK: 7 MiB in 16 packages
(1/5) Installing nghttp2-libs (1.35.1-r0)
(2/5) Installing libssh2 (1.8.2-r0)
(3/5) Installing libcurl (7.64.0-r2)
(4/5) Installing curl (7.64.0-r2)
(5/5) Installing deps (0)
Executing busybox-1.29.3-r10.trigger
OK: 8 MiB in 21 packages
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 37.4M  100 37.4M    0     0   550k      0  0:01:09  0:01:09 --:--:--  522k
(1/5) Purging deps (0)
(2/5) Purging curl (7.64.0-r2)
(3/5) Purging libcurl (7.64.0-r2)
(4/5) Purging nghttp2-libs (1.35.1-r0)
(5/5) Purging libssh2 (1.8.2-r0)
Executing busybox-1.29.3-r10.trigger
OK: 7 MiB in 16 packages
Removing intermediate container 00a41be6c337
 ---> 94ff3774735c
Step 4/4 : ENTRYPOINT []
 ---> Running in e460e1ac0f47
Removing intermediate container e460e1ac0f47
 ---> bbadada24a40
Successfully built bbadada24a40
Successfully tagged volcanosh/vk-admission-base:latest

[k82cn]

/lgtm
/approve

[volcano-sh-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: k82cn, TommyLike

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [k82cn]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment