possible early detach of fctx in resolver.c
In the ADB refactoring branch (!6033 (merged)) there was a single crash observed which indicates that the adb was destroyd while
dns_adb_createfind() was running. Since the fetch context holds a reference to the ADB, this implies that the fetch context must have been detached too soon. We decided not to hold up the MR for it, but we need to keep an eye out for recurrences.