Fix a use-after-free bug in dns_zonemgr_releasezone()
The dns_zonemgr_detach() function needs to write-lock 'zmgr' to avoid a race with dns_zonemgr_releasezone().
Closes #3768 (closed)
The dns_zonemgr_detach() function needs to write-lock 'zmgr' to avoid a race with dns_zonemgr_releasezone().
Closes #3768 (closed)