Set example timestamps to 2038-01-18T21:14:07Z

This timestamp is the last possible moment that can be represented on
32-bit systems as an integer.

As a consequence of revising the JSON examples, the corresponding PEM
files must be re-generated as well.

Change-Id: Ic6014c08b4545db036605beef1e6a8829ed347c4
Related-Bug: 1190054
Related-Bug: 1225084