when (re)priming the root, we do so with auth=0. We'll only set auth=1 after we have...

when (re)priming the root, we do so with auth=0. We'll only set auth=1 after we have an answer from the roots. This however opens up a small race condition in which the root is expired (ttl=0), but still auth=1 in the cache. Our attempt to replace it with auth=0 dta fails at that point. This is probably due to some fencepost error somewhere. To not be subtle about this, explicitly nuke the root when we reprime.

(cherry picked from commit 0d032a66afe508cc86a25eef26fc9be0867a117e)