fix: ensure daemon start successfully after update damon offline

[Ace-Tang]

Signed-off-by: Ace-Tang [email protected]

Ⅰ. Describe what this PR did

1. make Namespace field not marshal to config file to ensure daemon
   restart successful after update daemon offline.
2. add update daemon offline test.
3. fix update daemon error when config file is not exist.

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how you did it

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #1743 into master will decrease coverage by 0.73%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #1743      +/-   ##
=========================================
- Coverage   14.14%   13.4%   -0.74%     
=========================================
  Files         281     281              
  Lines       56755   58487    +1732     
=========================================
- Hits         8027    7842     -185     
- Misses      47805   49711    +1906     
- Partials      923     934      +11

Impacted Files	Coverage Δ
daemon/config/config.go	19.75% <ø> (ø)	⬆️
cli/update_daemon.go	0% <0%> (ø)	⬆️
daemon/mgr/container_envs.go	8.97% <0%> (-35.9%)	⬇️
pkg/utils/utils.go	61.73% <0%> (-28.01%)	⬇️
daemon/mgr/spec_process.go	45.18% <0%> (-22.6%)	⬇️
cri/v1alpha2/cri_utils.go	16.77% <0%> (-18.99%)	⬇️
daemon/mgr/container.go	34.56% <0%> (-17.91%)	⬇️
pkg/user/user.go	59.15% <0%> (-16.61%)	⬇️
cri/v1alpha1/cri_utils.go	19.28% <0%> (-15.64%)	⬇️
daemon/mgr/container_types.go	68.29% <0%> (-13.11%)	⬇️
... and 12 more

[rudyfly]

LGTM