[BUG] Enable and fix legacy maps tests

[kavilla]

Describe the bug
Origin:
https://github.com/opensearch-project/OpenSearch-Dashboards/pull/233/files

This tests were removed because at the time we didn't have a dedicated maps service but now that we do we can mock up some example responses that the tests are expecting.

To Reproduce
Remove the legacy map from Jest ignore and run yarn test:jest src/plugins/maps_legacy and watch failures

Expected behavior
Tests to passing

Additional context
#2042 introduces new logic that we can add more tests for.