btrfs: make btrfs_release_delayed_iref handle the !iref case

Right now we only cleanup the delayed iref if we have
BTRFS_DELAYED_NODE_DEL_IREF set on the node.  However we have some error
conditions that need to cleanup the iref if it still exists, so to make
this code cleaner move the test_bit into btrfs_release_delayed_iref
itself and unconditionally call it in each of the cases instead.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>