Kibana version: 7.8

Describe the bug: When processing a saved object import that results in reference errors, the error count is inaccurate.

Steps to reproduce:

1. Start Kibana and load up eCommerce sample data
2. Delete the index pattern
3. Export the Dashboard, including references
4. Import the new NDJSON file

Expected behavior: The error count should equal 9, instead it appears to be 16.

Screenshots (if relevant):

"Import saved objects" flyout:

Debugging and checking the object state reveals that several duplicates of import objects are included: