If two key refreshes are triggered (using "rndc managed-keys refresh")
and completed within the same second and both receive successfully
validated, identical responses that do not cause a new key to be added
or an already existing key to be removed, the following message will be
logged:

    21-Nov-2017 11:45:03.871 managed-keys-zone: error during managed-keys processing (no more): DNSSEC validation may be at risk

This message should be suppressed, because the sequence of events
causing it to be logged is harmless to DNSSEC validation.