DNSSEC refresh change log entry unnecessary if no keys are refreshed

[rawlinp]

This Improvement request (usability, performance, tech debt, etc.) affects these Traffic Control components:

• Traffic Ops

Current behavior:

When making a request to /cdns/dnsseckeys/refresh, a change log entry is created even if there were no DNSSEC keys refreshed:

Refreshed 0 DNSSEC keys

New behavior:

If 0 DNSSEC keys are refreshed via a request to /cdns/dnsseckeys/refresh, a change log entry should not be created. While it's nice to know that the cron job is working, this is mostly useless information. A change log entry is really only necessary if any keys are actually refreshed.