As part of indirect reference resolution in prepared transactions, the transaction operation structure currently always refer the first update in the update chain. This assumption is wrong, first update might be from a different transaction in case of lower isolation levels.

So, need to ensure the update pointed by the transaction op is generated from this transaction itself.

Below is the bug reported:
test/format aborts with following assert.

t: process 29357
[1538620481:971700][29357:0x7f468cb49700], t, WT_SESSION.reset: __wt_txn_release_resources, 1281: txn->multi_update_count == 0
[1538620481:971729][29357:0x7f468cb49700], t, WT_SESSION.reset: __wt_abort, 30: aborting WiredTiger library
Aborted (core dumped)

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1. RUN PARAMETERS
   ############################################
   abort=0
   alter=0
   auto_throttle=1
   backups=1
   bitcnt=1
   bloom=1
   bloom_bit_count=59
   bloom_hash_count=22
   bloom_oldest=0
   cache=61
   cache_minimum=0
   checkpoints=wiredtiger
   checkpoint_log_size=46
   checkpoint_wait=75
   checksum=on
   chunk_size=5
   compaction=0
   compression=none
   data_extend=0
   data_source=table
   delete_pct=54
   dictionary=0
   direct_io=0
   encryption=none
   evict_max=0
   file_type=variable-length column-store
   firstfit=0
   huffman_key=0
   huffman_value=0
   independent_thread_rng=0
   in_memory=0
   insert_pct=21
   internal_key_truncation=1
   internal_page_max=9
   isolation=random
   key_gap=3
   key_max=103
   key_min=12
   leaf_page_max=17
   leak_memory=0
   logging=0
   logging_archive=1
   logging_compression=none
   logging_file_max=125400
   logging_prealloc=0
   long_running_txn=0
   lsm_worker_threads=4
   memory_page_max=4
   merge_max=9
   mmap=1
   modify_pct=25
   ops=50000
   prefix_compression=1
   prefix_compression_min=8
   prepare=1
   quiet=1
   read_pct=0
   rebalance=1
   repeat_data_pct=13
   reverse=0
   rows=10000
   runs=1
   salvage=1
   split_pct=67
   statistics=0
   statistics_server=0
   threads=4
   timer=360
   timing_stress_checkpoint=0
   timing_stress_lookaside_sweep=0
   timing_stress_split_1=0
   timing_stress_split_2=0
   timing_stress_split_3=0
   timing_stress_split_4=0
   timing_stress_split_5=0
   timing_stress_split_6=0
   timing_stress_split_7=0
   timing_stress_split_8=0
   transaction_timestamps=1
   transaction-frequency=71
   truncate=1
   value_max=1113
   value_min=12
   verify=1
   wiredtiger_config=
   write_pct=0
   ############################################