RFR: 8337951: Test sun/security/validator/samedn.sh CertificateNotYetValidException: NotBefore validation

[Fernando Guallini]

The test sun/security/validator/samedn.sh failed once due to the following reason:

`Caused by: java.security.cert.CertificateNotYetValidException: NotBefore: Tue Aug 06 14:41:13 GMT 2024`

This test generates several certificates using the keytool as a precondition, and then validates their certificate paths.

This failure is very rare and could not be reproduced. However, based on the failure logs, the test finished at **14:41:12**, while the test certificate's NotBefore time was set to **14:41:13**. It is possible that when the certificate was created, keytool **rounded up** the NotBefore time to the nearest second. As a result, the test may have validated the certificate just before it became valid.

The proposed fix is to set the NotBefore time to one minute in the past, ensuring the certificate will be valid when running the test.

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Commit messages:
 - cert startdate 1 minute ago

Changes: https://git.openjdk.org/jdk/pull/20728/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20728&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337951
  Stats: 5 lines in 1 file changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20728.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20728/head:pull/20728

PR: https://git.openjdk.org/jdk/pull/20728