[WIP] test removing the update ignore to see what fails.

This is fundamentally risky - we don't know all the reasons why UPDATE IGNORE could fail & hence
we don't know what could be deleted when it does. Note that I came across the following as a deadlock-causing query

 DELETE FROM civicrm_contact WHERE  primary_contact_id = 41372076

and am altering the test to look for whether UPDATE IGNORE is in fact needed as the above looks risky
as well as increasing our lock queries

CRM/Dedupe/Merger.php

@@ -477,6 +477,8 @@ public static function removeContactBelongings($otherID, $tables) {
    * @param bool $tables
    * @param array $tableOperations
    * @param array $customTableToCopyFrom
+   *
+   * @throws \CiviCRM_API3_Exception
    */
   public static function moveContactBelongings($mainId, $otherId, $tables = FALSE, $tableOperations = [], $customTableToCopyFrom = NULL) {
     $cidRefs = self::cidRefs();
@@ -558,15 +560,13 @@ public static function moveContactBelongings($mainId, $otherId, $tables = FALSE,
             // run this INSERT for ContactReference fields
             $sqls[] = "INSERT INTO $table ($field) VALUES ($mainId)";
           }
-          $sqls[] = "UPDATE IGNORE $table SET $field = $mainId WHERE $field = $otherId";
-          $sqls[] = "DELETE FROM $table WHERE $field = $otherId";
+          $sqls[] = "UPDATE $table SET $field = $mainId WHERE $field = $otherId";
         }
       }
 
       if (isset($eidRefs[$table])) {
         foreach ($eidRefs[$table] as $entityTable => $entityId) {
-          $sqls[] = "UPDATE IGNORE $table SET $entityId = $mainId WHERE $entityId = $otherId AND $entityTable = 'civicrm_contact'";
-          $sqls[] = "DELETE FROM $table WHERE $entityId = $otherId AND $entityTable = 'civicrm_contact'";
+          $sqls[] = "UPDATE $table SET $entityId = $mainId WHERE $entityId = $otherId AND $entityTable = 'civicrm_contact'";
         }
       }
     }