multisnapshotter: set snapshotter in container config

[Ace-Tang]

since we support multi snapshotter, set current snapshotter in container
config, then plugin can know current used snapshotter.

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

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)? (你真的觉得不需要加测试吗？)

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Merging #2739 into master will decrease coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2739      +/-   ##
==========================================
- Coverage   69.42%   69.33%   -0.09%     
==========================================
  Files         278      278              
  Lines       17443    17447       +4     
==========================================
- Hits        12109    12097      -12     
- Misses       4014     4024      +10     
- Partials     1320     1326       +6

Flag	Coverage Δ
#criv1alpha2_test	39.5% <100%> (+0.08%)	⬆️
#integration_test_0	36.62% <100%> (+0.03%)	⬆️
#integration_test_1	35.52% <100%> (ø)	⬆️
#integration_test_2	36.55% <100%> (-0.01%)	⬇️
#integration_test_3	35.38% <100%> (+0.02%)	⬆️
#node_e2e_test	35.31% <100%> (-0.12%)	⬇️
#unittest	28.43% <0%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
daemon/mgr/container.go	61.16% <100%> (+0.37%)	⬆️
cri/ocicni/cni_manager.go	58.82% <0%> (-11.77%)	⬇️
daemon/logger/jsonfile/utils.go	71.54% <0%> (-1.63%)	⬇️
daemon/mgr/spec_linux.go	78.77% <0%> (-1.08%)	⬇️
ctrd/container.go	56.89% <0%> (-0.77%)	⬇️
cri/v1alpha2/cri.go	71.75% <0%> (-0.39%)	⬇️

[fuweid]

LGTM. Wait for UI.