kubernetes/pkg/kubelet/certificate/bootstrap/testdata/README.md

Keys in this directory are generated for testing purposes only.

In this pr validCert(mycertvalid.crt):
```
Validity
Not Before: Apr 26 23:26:52 2017 GMT
Not After : Apr 2 23:26:52 2117 GMT
```



InvalidCert(mycertinvalid.crt):
```
Validity
Not Before: Dec 16 06:46:25 2014 GMT
Not After : Dec 16 06:46:25 2015 GMT
```