fix misspell in pouchd in doc and code

[wgliang]

Ⅰ. Describe what this PR did

fix misspell in pouchd in doc and code

Ⅱ. Does this pull request fix one issue?

fix #1108

Ⅲ. Describe how you did it

Ⅳ. Describe how to verify it

all test

Ⅴ. Special notes for reviews

@allencloud

[pouchrobot]

@wgliang Thanks for your contribution. 🍻
Please sign off in each of your commits.

[pouchrobot]

We found this is your first time to contribute to Pouch, @wgliang
👏 We really appreciate it.
Just remind that you have read the contribution guide: https://github.com/alibaba/pouch/blob/master/CONTRIBUTING.md
If you didn't, you should do that first. If done, welcome again and please enjoy hacking! 🍻

[CLAassistant]

All committers have signed the CLA.

[HusterWan]

LGTM

[pouchrobot]

ping @wgliang

CI fails according integration system.
Please refer to the CI failure Details button to corresponding test, and update your PR to pass CI.

If this is flaky test, welcome to track this with profiling an issue.

build url: https://travis-ci.org/alibaba/pouch/builds/369696337
build duration: 1842s

[HusterWan]

This PR is not the reason why cri test failed
@YaoZengzeng may be you should check why pull image failed

@wgliang 🥂 thanks a lot for works !!!

[wgliang]

Cool, efficiency is really high!

[wgliang]

Thanks for all pouchers!