[9.18] fix: usr: Raise the log level of priming failures
When a priming query is complete, it's currently logged at level ISC_LOG_DEBUG(1), regardless of success or failure. We are now raising it to ISC_LOG_NOTICE in the case of failure. [GL #3516 (closed)]
Closes #3516 (closed)
Backport of MR !9121 (merged)