Adds tests to new empty and error states

app/assets/javascripts/commit/pipelines/pipelines_table.js

...javascripts/vue_pipelines_index/components/empty_state.js

...javascripts/vue_pipelines_index/components/error_state.js

...scripts/vue_pipelines_index/components/navigation_tabs.js

app/assets/javascripts/vue_pipelines_index/pipelines.js

app/views/projects/commit/_pipelines_list.haml

app/views/projects/pipelines/index.html.haml

spec/features/projects/pipelines/pipelines_spec.rb

spec/javascripts/commit/pipelines/pipelines_spec.js

spec/javascripts/fixtures/pipelines.html.haml

spec/javascripts/vue_pipelines_index/empty_state_spec.js

spec/javascripts/vue_pipelines_index/error_state_spec.js

spec/javascripts/vue_pipelines_index/mock_data.js

spec/javascripts/vue_pipelines_index/nav_controls_spec.js

spec/javascripts/vue_pipelines_index/pipelines_spec.js