conf: Remove console stream callback only when freeing console helper

conf: Remove console stream callback only when freeing console helper

Commit ba226d334acbc49f6751b430e0c4e00f69eef6bf tried to fix crash of
the daemon when a domain with an open console was destroyed. The fix was
wrong as it tried to remove the callback also when the stream was
aborted, where at that point the fd stream driver was already freed and
removed.

This patch clears the callbacks with a helper right before the hash is
freed, so that it doesn't interfere with other codepaths where the
stream object is freed.