have write lock before setting RDATASET_ATTR_STALE in mark_header_stale

76 jobs for !2775 with 1475-threadsanitizer-data-race-lib-dns-rbtdb-c-1545-in-mark_header_stale-and-check_stale_header in 27 minutes and 54 seconds (queued for 1 minute and 5 seconds)
merge request