When named starts it creates an empty KEYDATA record in the managed-keys
zone as a placeholder, then schedules a key refresh. If key refresh
fails for some reason (e.g. connectivity problems), named will load the
placeholder key into secroots as a trusted key during the next startup,
which will break the chain of trust, and named will never recover from
that state until managed-keys.bind and managed-keys.bind.jnl files are
manually deleted before (re)starting named again.
Before calling load_secroots(), check that we are not dealing with a
placeholder.
354ae2d7e3