refactor: refactor return err for golint

[oblivionfallout]

Ⅰ. Describe what this PR did

For Go Report. daemon/mgr/container.go has a golint issue. Remove if and just return err.

Ⅱ. Does this pull request fix one issue?

fixes one part of #964

Ⅲ. Describe how you did it

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[CLAassistant]

All committers have signed the CLA.

[codecov-io]

Codecov Report

Merging #1117 into master will decrease coverage by 0.12%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #1117      +/-   ##
==========================================
- Coverage   16.44%   16.31%   -0.13%     
==========================================
  Files         165      165              
  Lines        8841     8842       +1     
==========================================
- Hits         1454     1443      -11     
- Misses       7283     7295      +12     
  Partials      104      104

Impacted Files	Coverage Δ
daemon/mgr/container.go	5% <0%> (ø)	⬆️
pkg/utils/utils.go	78.12% <0%> (+2.48%)	⬆️
daemon/containerio/raw_file.go	4.16% <0%> (+4.16%)	⬆️
pkg/kernel/kernel.go	83.33% <0%> (+10.6%)	⬆️

[allencloud]

LGTM, thanks a lot for your contribution.