Fix timestamp being invalid if nanoseconds component is zero

[rosstitmarsh]

Closes #3463

I am not familiar enough with Java and this project to add a test for it but I verified that it fixed the bug and that all the existing tests passed. Please add them if you think it is needed before merging.

Checklist

• Testing:

  • The feature has automated tests
  • Tests were run
  • If not, explain how you tested your changes
    • Used the PV that I noticed the bug with that always has a 0 nanoseconds component to see if the timestamp shown correctly

• Documentation:

  • The feature is documented
  • The documentation is up to date
  • Release notes:
    • Added an entry if the change is breaking or significant
    • Added an entry when adding a new feature

[kasemir]

Thanks!