Increase unit test coverage

[lcarva]

For the most part, the important code paths in this repo are well covered. However, there are a few statements in a handful of files that could benefit from additional testing.

NOTE: The goal here is not to achieve 100% test coverage since this can be quite daunting in Go due how errors are handled.

Acceptance Criteria

• Increase unit test coverage of the non-error error handling statements in the following files:
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/cmd%2Finspect%2Finspect_policy.go
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/internal%2Fattestation%2Fattestation.go
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/internal%2Fevaluation_target%2Fapplication_snapshot_image%2Fapplication_snapshot_image.go
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/internal%2Foutput%2Foutput.go
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/internal%2Fapplicationsnapshot%2Freport.go
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/internal%2Ftracker%2Ftracker.go
  • https://app.codecov.io/gh/enterprise-contract/ec-cli/blob/main/internal%2Fopa%2Frule%2Frule.go