Before change
```
=== Failed
=== FAIL: datasource/hcp-packer-iteration TestAccDatasource_HCPPackerIteration (1.97s)
pluginacc.go:143: Error running plugin acceptance tests: Bad exit code. Logfile: packer_log_hcp_packer_iteration_datasource_basic_test.txt
Logs can be found at /Users/wilkenrivera/Development/packer/datasource/hcp-packer-iteration/packer_log_hcp_packer_iteration_datasource_basic_test.txt
and the acceptance test template can be found at /Users/wilkenrivera/Development/packer/datasource/hcp-packer-iteration/hcp_packer_iteration_datasource_basic_test.pkr.hcl
DONE 690 tests, 5 skipped, 1 failure in 387.912s
```
After change
```
=== SKIP: datasource/hcp-packer-iteration TestAccDatasource_HCPPackerIteration (0.00s)
data_acc_test.go:35: Acceptance tests skipped unless envs "HCP_CLIENT_ID" and "HCP_CLIENT_SECRET" are set
```
create a null data source for testing. We can choose to document if we want to, but it's a convenience for us
add a test to catch cyclic datasource dependency, update tests to include out of order data sources, and update the code to clean up the returned diagnostics generated from the recursive evaluation
PR review comments
Wilken Rivera
Megan Marsh
Sylvia MossandAdrien Delorme