improve the coverage of yurtappdaemon

[River-sh]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line: /kind enhancement

What this PR does / why we need it:

this PR is used to improve the unite test caverage of yurtappdaemon about workload operator(eg. create, update,delete)

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

```release-note NONE ``` #### other Note

[openyurt-bot]

@River-sh: GitHub didn't allow me to assign the following users: your_reviewer.

Note that only openyurtio members, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time. For more information please see the contributor guide

In response to [this](https://github.com/openyurtio/yurt-app-manager/pull/120): > > > >#### What type of PR is this? >> Uncomment only one ` /kind <>` line, hit enter to put that in a new line, and remove leading whitespace from that line: >> /kind enhancement > > >#### What this PR does / why we need it: > >#### Which issue(s) this PR fixes: > >Fixes # > >#### Special notes for your reviewer: > > > >#### Does this PR introduce a user-facing change? > >```release-note > >``` > >#### other Note > > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[codecov[bot]]

Codecov Report

Merging #120 (bdd504d) into master (7c799d4) will increase coverage by 0.90%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #120      +/-   ##
==========================================
+ Coverage   37.37%   38.27%   +0.90%     
==========================================
  Files          42       42              
  Lines        4776     4776              
==========================================
+ Hits         1785     1828      +43     
+ Misses       2752     2704      -48     
- Partials      239      244       +5     

Flag	Coverage Δ
unittests	38.27% <ø> (+0.90%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...daemon/workloadcontroller/deployment_controller.go	64.92% <0.00%> (+32.08%)	:arrow_up:

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[rambohe-ch]

/lgtm /approve

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rambohe-ch, River-sh

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](https://github.com/openyurtio/yurt-app-manager/blob/master/OWNERS)~~ [rambohe-ch] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rambohe-ch, River-sh

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](https://github.com/openyurtio/yurt-app-manager/blob/master/OWNERS)~~ [rambohe-ch] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment