Btrfs: don't ignore errors from btrfs_run_delayed_items

tree-log.c was ignoring the return value from btrfs_run_delayed_items()
in several places.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>