ocfs2: goto out_unlock if ocfs2_get_clusters_nocache() failed in ocfs2_fiemap()

Last time we found there is lock/unlock bug in ocfs2_file_aio_write, and
then we did a thorough search for all lock resources in
ocfs2_inode_info, including rw, inode and open lockres and found this
bug.  My kernel version is 3.0.13, and it is also in the lastest version
3.9.  In ocfs2_fiemap, once ocfs2_get_clusters_nocache failed, it should
goto out_unlock instead of out, because we need release buffer head, up
read alloc sem and unlock inode.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Reviewed-by: Jie Liu <jeff.liu@oracle.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Acked-by: Sunil Mushran <sunil.mushran@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>