xfs: check correct status variable for xfs_inobt_get_rec() call

The call to xfs_inobt_get_rec() in xfs_dialloc_ag() passes 'j' as
the output status variable. The immediately following
XFS_WANT_CORRUPTED_GOTO() checks the value of 'i,' which is from
the previous lookup call and has already been checked. Fix the
corruption check to use 'j.'

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>