clang tidy generates use-after-move warning

clang tidy generates use-after-move warning

clang-tidy original warning:
/home/suyash/ceph/src/cls/queue/cls_queue_src.cc:330:50: warning: 'bl' used after it was moved [bugprone-use-after-move]
    uint64_t entry_start_offset = start_offset - bl.length();
                                                 ^
/home/suyash/ceph/src/cls/queue/cls_queue_src.cc:333:14: note: move occurred here
    bl_chunk = std::move(bl);
             ^
/home/suyash/ceph/src/cls/queue/cls_queue_src.cc:330:50: note: the use happens in a later loop iteration than the move
    uint64_t entry_start_offset = start_offset - bl.length();
                                                 ^

Fixes: https://tracker.ceph.com/issues/66356
Signed-off-by: Suyash Dongre <suyashd999@gmail.com>