Calling stream_t::destroy from the stream_t::on_read callback will
block the thread in watcher_t::remove because the FD is currently "in
callback". A similar issue was fixed in the lookip plugin with
961409b668 ("lookip: Disconnect asynchronously to avoid dead-locking
watcher unregistration").
Fixes: 85ebf6abd4 ("whitelist: Add error handling to socket reads and fix a memory leak")
seantywork