Changing ModelBase.save to correct updated time

This change modifies the updated_at time property for new ModelBase
objects. When the save method is called for a new object that does not yet
have an id assigned, the created_at and updated_at times are set to the
same value.

Changes
* modified ModelBase.save method for new objects
* adding a test to confirm new secrets have the same created_at and
  updated_at times

Change-Id: I3a64c05fdc21dd3e07852aa750ea4c099564da65
Closes-Bug: #1382188
Merge "Changing ModelBase.save to correct updated time"