xfs: fix unlock in xfs_bmap_add_attrfork

xfs: fix unlock in xfs_bmap_add_attrfork

xfs_trans_ijoin() activates the inode in a transaction and
also can specify which lock to free when the transaction is
committed or canceled.

xfs_bmap_add_attrfork call locks and adds the lock to the
transaction but also manually removes the lock. Change the
routine to not add the lock to the transaction and manually
remove lock on completion.

While here, clean up the xfs_trans_cancel flags and goto names.

Signed-off-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ben Myers <bpm@sgi.com>