ocfs2/trivial: Code cleanup for allocation reservation.

Two tiny cleanup for allocation reservation.
1. Remove some extra codes in ocfs2_local_alloc_find_clear_bits.
2. Remove an unuseful variables in ocfs2_find_resv_lhs.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>