fix: support nullable bool value set in config

[Ace-Tang]

make nullable value like false and 0 not be recognized as
empry value, in config set, they should be valid value.

Signed-off-by: Ace-Tang aceapril@126.com

Ⅰ. Describe what this PR did

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 #1502 into master will decrease coverage by 0.91%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #1502      +/-   ##
==========================================
- Coverage   40.56%   39.64%   -0.92%     
==========================================
  Files         254      254              
  Lines       16537    16891     +354     
==========================================
- Hits         6708     6697      -11     
- Misses       8966     9329     +363     
- Partials      863      865       +2

Impacted Files	Coverage Δ
pkg/utils/utils.go	85.27% <0%> (-0.36%)	⬇️
daemon/mgr/spec_mount.go	54.54% <0%> (-15.67%)	⬇️
apis/server/utils.go	59.52% <0%> (-4.77%)	⬇️
ctrd/watch.go	75% <0%> (-3.13%)	⬇️
daemon/mgr/network.go	68.94% <0%> (-0.49%)	⬇️
daemon/mgr/container.go	49.2% <0%> (-0.09%)	⬇️
cri/v1alpha2/cri.go	0% <0%> (ø)	⬆️
cri/v1alpha1/cri.go	0% <0%> (ø)	⬆️

[rudyfly]

LGTM