[YSQL] Foreign key check doesn't set ROW_MARK_KEYSHARE rowmark

[d-uspenskiy]

It was found that read RPC for FK check comes without rowmark field:

I1021 01:49:10.540298 11423 tablet_service.cc:1707] Received Read RPC: tablet_id: "9b31c78009394c6fa06bc89931da189e"
include_trace: false                  
consistency_level: STRONG             
transaction {                         
  transaction_id: "[\260\256\264Gz@R\222g\310\003\033\221_\327"
  isolation: SNAPSHOT_ISOLATION 
  status_tablet: "dd76b6ef50bd4e4b92c84bd4dbe3e0f9"
  priority: 10287815725710478686
  start_hybrid_time: 6566891317279817728
}                                     
propagated_hybrid_time: 6566891317411524608
read_time {                           
  read_ht: 6566891317279817728  
  local_limit_ht: 6566891317484617728
  global_limit_ht: 6566891317484617728
  in_txn_limit_ht: 6566891317406429184
}                                     
pgsql_batch {                         
  client: YQL_CLIENT_PGSQL      
  stmt_id: 54887024                   
  schema_version: 0                   
  hash_code: 4624                     
  targets {                           
    column_id: -8                     
  }                                   
  table_id: "000030a9000030008000000000004001"
  ybctid_column_value {               
    value {                           
      binary_value: "G\022\020H\200\000\000\001!!"
    }                                 
  }                                   
  batch_arguments {                   
    order: 0                          
    ybctid {                          
      value {                         
        binary_value: "G\022\020H\200\000\000\001!!"
      }                               
    }                                 
  }                                   
  unknown_ybctid_allowed: true   
}                                     
proxy_uuid: ""                        
DEPRECATED_may_have_metadata: true
rejection_score: 0                    
batch_idx: 18446744073709551615