bugfix: fix containerd pid may be reuse

[HusterWan]

Signed-off-by: Michael Wan zirenwan@gmail.com

Ⅰ. Describe what this PR did

In case containerd process may still alive on the host when the pouchd starting, we cache the containerd pid in a file container.pid and the pid file will be deleted when the pouchd exited.

In this case, we can check if the pid of containerd still alive, if true pouchd will not run a new containerd instance, but just take over the old containerd instance.

But there has a situation that the pid file cannot be deleted that the host was broken down by accident, and when the host restart again the pid file record a pid reused by the other process but the containerd. So when the pouchd restarting, it will check the containerd is alived but cannot take over the process because the process is not the containerd.

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？)

add PouchDaemonSuite.TestContainerdPIDReuse

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Merging #2679 into master will decrease coverage by 0.06%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #2679      +/-   ##
==========================================
- Coverage   69.19%   69.13%   -0.07%     
==========================================
  Files         278      278              
  Lines       17392    17415      +23     
==========================================
+ Hits        12035    12040       +5     
- Misses       4028     4048      +20     
+ Partials     1329     1327       -2

Flag	Coverage Δ
#criv1alpha2_test	39.2% <0%> (-0.16%)	⬇️
#integration_test_0	36.27% <0%> (+0.04%)	⬆️
#integration_test_1	35.19% <0%> (+0.02%)	⬆️
#integration_test_2	36.58% <0%> (+0.27%)	⬆️
#integration_test_3	35.11% <0%> (-0.04%)	⬇️
#node_e2e_test	34.98% <0%> (-0.05%)	⬇️
#unittest	27.36% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
ctrd/supervisord/daemon.go	49.06% <0%> (-8.18%)	⬇️
daemon/mgr/spec_linux.go	77.3% <0%> (-0.99%)	⬇️
cri/v1alpha2/cri.go	71.26% <0%> (ø)	⬆️
daemon/mgr/container.go	59.24% <0%> (+0.21%)	⬆️
ctrd/container.go	57.66% <0%> (+1.14%)	⬆️

[rudyfly]

LGTM