Store reports fix exception

What does this MR do?

For .gitlab-ci.yml:

image: alpine

all_reports:
  script: echo Hello World
  only:
    - master
  artifacts:
    reports:
      codequality: gl-code-quality-report.json
      container_scanning: gl-container-scanning-report.json
      dast: gl-dast-report.json
      dependency_scanning: gl-dependency-scanning-report.json
      license_management: gl-license-management-report.json
      sast: gl-sast-report.json
      performance: performance.json

It fixes:

2018-11-05T15:54:55.987Z 6 TID-gmowf9gm2 WARN: ArgumentError:  must be a String or Symbol
2018-11-05T15:54:55.987Z 6 TID-gmowf9gm2 WARN: /data/cache/bundle/gems/flipper-0.13.0/lib/flipper/dsl.rb:172:in `feature'
/home/git/gitlab/lib/feature.rb:31:in `get'
/home/git/gitlab/lib/feature.rb:48:in `enabled?'
/home/git/gitlab/ee/app/models/ee/project.rb:590:in `licensed_feature_available?'
/home/git/gitlab/ee/app/models/ee/project.rb:268:in `feature_available?'
/home/git/gitlab/ee/app/models/ee/ci/build.rb:47:in `block in collect_security_reports!'
/home/git/gitlab/app/models/ci/build.rb:741:in `block (2 levels) in each_report'
/home/git/gitlab/lib/gitlab/ci/build/artifacts/adapters/raw_stream.rb:22:in `each_blob'

We do not consume errors yet, so lets for now provide an interface for them.

What are the relevant issue numbers?

Not yet reported.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides