Issue #2250429 by ultimike, chx: D6_block migration not migrating all blocks.

...ib/Drupal/migrate/Plugin/migrate/process/DedupeEntity.php

...e/tests/Drupal/migrate/Tests/process/DedupeEntityTest.php

...rate_drupal/config/install/migrate.migration.d6_block.yml

...ig/install/migrate.migration.d6_upload_field_instance.yml

.../Drupal/migrate_drupal/Plugin/migrate/source/d6/Block.php

...pal/lib/Drupal/migrate_drupal/Tests/Dump/Drupal6Block.php

...rupal/lib/Drupal/migrate_drupal/Tests/Dump/Drupal6Box.php

...l/lib/Drupal/migrate_drupal/Tests/d6/MigrateBlockTest.php

...Drupal/migrate_drupal/Tests/d6/MigrateCustomBlockTest.php

...pal/migrate_drupal/Tests/d6/MigrateUploadInstanceTest.php