We have added discontig block group now, and now an inode
can be allocated in an discontig block group. So get
it in ocfs2_get_suballoc_slot_bit.

The old ocfs2_test_suballoc_bit gets group block no
from the allocation inode which is wrong. Fix it by
passing the right group.
Acked-by: NMark Fasheh <mfasheh@suse.com>
Signed-off-by: NTao Ma <tao.ma@oracle.com>