fixes #24571 - support private keys from new google developer console
[JENKINS-24571] - support private keys from new google developer console - improved upgrade process of legacy credentials
[JENKINS-24571] - support private keys from new google developer console - changes after review - part 1
Merge pull request #3 from DavidHamm/JENKINS-24571

fixes #24571 - support private keys from new google developer console