[PDI-11359] Version dates do not change

Forward port of Regression [SP-1090]
Timestamp for jobs in DI repository continuously displays the same value for different versions.
Fixed by creating new timestamp at check-in of JCR File.

http://jira.pentaho.com/browse/PDI-11359
http://jira.pentaho.com/browse/SP-1090
Merge pull request #1290 from hudak/PDI-11359

[PDI-11359] Version dates do not change