Limit the frequency of updates to cwd_token.last_acccesed_time

Every time a token is validated, the value of cwd_token.last_accessed_time is updated. This field has a resolution of milliseconds which is very high for most use cases. By reducing the resolution we could reduce the number of times this field is updated and saved to the database.

This is important because any read-only request (like finding a user) via the REST API is authenticated, and Crowd refreshes the last_accessed_time, which is a write in the database. That means that read operations actually involve at least one write to the database, which is typically more expensive and less scalable.