harbor based-event preheat error

[hongfeioo]

Bug report:

[root@sgp2-test-k8s-slave01-202009 ~]# docker tag micr-dev.cloud.cn/df/g:v6  micr-dev.cloud.cn/df/g:v19
[root@sgp2-test-k8s-slave01-202009 ~]# docker push !$
docker push micr-dev.cloud.cn/df/g:v19
The push refers to repository [micr-dev.cloud.cn/df/g]
5f70bf18a086: Layer already exists
4b26ab29a475: Layer already exists
ccb1d68e3fb7: Layer already exists
e387107e2065: Layer already exists
63bf84221cce: Layer already exists
e02dce553481: Layer already exists
dea2e4984e29: Layer already exists
v19: digest: sha256:b1f5935eb2e9e2ae89c0b3e2e148c19068d91ca502e857052f14db230443e4c2 size: 3012

预热成功

[root@sgp2-test-k8s-slave01-202009 ~]# docker tag  micr-dev.cloud.cn/df/g:v19     micr-dev.cloud.cn/df/g:v20
[root@sgp2-test-k8s-slave01-202009 ~]# docker push !$
docker push micr-dev.cloud.cn/df/g:v20
The push refers to repository [micr-dev.cloud.cn/df/g]
5f70bf18a086: Layer already exists
4b26ab29a475: Layer already exists
ccb1d68e3fb7: Layer already exists
e387107e2065: Layer already exists
63bf84221cce: Layer already exists
e02dce553481: Layer already exists
dea2e4984e29: Layer already exists
v20: digest: sha256:b1f5935eb2e9e2ae89c0b3e2e148c19068d91ca502e857052f14db230443e4c2 size: 3012

预热失败，

经过反复尝试，没有发现什么规律， 同一个镜像因为打了不同的tag就会出现有可能预热失败的情况。 

Expected behavior:

同一个镜像应该无论使用哪个tag都应该可以预热成功

How to reproduce it:

Environment:

• Dragonfly version:
  NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION dragonfly dragonfly-system 3 2021-12-06 20:17:16.621876558 +0800 CST deployed dragonfly-0.5.21 0.5.21
• OS:
  linux
• Kernel (e.g. uname -a):
  5.4.54-1.0.0.std7c.el7.2.x86_64 #1 SMP Mon Nov 16 10:02:20 CST 2020 x86_64 x86_64 x86_64 GNU/Linux
• Others:
  cdn.log

[gaius-qi]

CDN download task 096099195aa1d7050cba032f68075c0f91c0167d172c62fecf12b6ae7eb9ac2a failed. @244372610

{"level":"info","ts":"2021-12-09 06:39:00.166","caller":"rpcserver/rpcserver.go:118","msg":"seeds task 096099195aa1d7050cba032f68075c0f91c0167d172c62fecf12b6ae7eb9ac2a result success: false"}