btrfs: calculate correct amount of space for delayed reference when evicting

When evicting an inode, we are incorrectly calculating the amount of space
required for a single delayed reference in case the free space tree is
enabled. We have to multiply by 2 the result of
btrfs_calc_insert_metadata_size(). We should be calculating according to
the size update and space release of the delayed block reserve logic at
btrfs_update_delayed_refs_rsv() and btrfs_delayed_refs_rsv_release().

Fix this by using the btrfs_calc_delayed_ref_bytes() helper at
evict_refill_and_join() instead of btrfs_calc_insert_metadata_size().

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