No need to set cache:key if no path was specified

Feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9666/diffs#note_24607518

lib/gitlab/ci/config/entry/cache.rb

@@ -25,10 +25,6 @@ module Gitlab
 
           helpers :key
 
-          def self.default
-            { key: Entry::Key.default }
-          end
-
           def value
             super.merge(key: key_value)
           end

spec/lib/ci/gitlab_ci_yaml_processor_spec.rb

@@ -51,7 +51,7 @@ module Ci
           commands: "pwd\nrspec",
           coverage_regex: nil,
           tag_list: [],
-          options: { cache: { key: 'default' } },
+          options: {},
           allow_failure: false,
           when: "on_success",
           environment: nil,
@@ -468,8 +468,7 @@ module Ci
           tag_list: [],
           options: {
             image: "ruby:2.1",
-            services: ["mysql"],
-            cache: { key: 'default' }
+            services: ["mysql"]
           },
           allow_failure: false,
           when: "on_success",
@@ -498,8 +497,7 @@ module Ci
           tag_list: [],
           options: {
             image: "ruby:2.5",
-            services: ["postgresql"],
-            cache: { key: 'default' }
+            services: ["postgresql"]
           },
           allow_failure: false,
           when: "on_success",
@@ -740,7 +738,6 @@ module Ci
           options: {
             image: "ruby:2.1",
             services: ["mysql"],
-            cache: { key: 'default' },
             artifacts: {
               name: "custom_name",
               paths: ["logs/", "binaries/"],
@@ -950,7 +947,7 @@ module Ci
             commands: "test",
             coverage_regex: nil,
             tag_list: [],
-            options: { cache: { key: 'default' } },
+            options: {},
             when: "on_success",
             allow_failure: false,
             environment: nil,
@@ -996,7 +993,7 @@ module Ci
             commands: "execute-script-for-job",
             coverage_regex: nil,
             tag_list: [],
-            options: { cache: { key: 'default' } },
+            options: {},
             when: "on_success",
             allow_failure: false,
             environment: nil,
@@ -1009,7 +1006,7 @@ module Ci
             commands: "execute-script-for-job",
             coverage_regex: nil,
             tag_list: [],
-            options: { cache: { key: 'default' } },
+            options: {},
             when: "on_success",
             allow_failure: false,
             environment: nil,

spec/lib/gitlab/ci/config/entry/job_spec.rb

@@ -144,8 +144,7 @@ describe Gitlab::Ci::Config::Entry::Job do
                    script: %w[rspec],
                    commands: "ls\npwd\nrspec",
                    stage: 'test',
-                   after_script: %w[cleanup],
-                   cache: { key: 'default' })
+                   after_script: %w[cleanup])
         end
       end
     end

spec/lib/gitlab/ci/config/entry/jobs_spec.rb

@@ -62,13 +62,11 @@ describe Gitlab::Ci::Config::Entry::Jobs do
           rspec: { name: :rspec,
                    script: %w[rspec],
                    commands: 'rspec',
-                   stage: 'test',
-                   cache: { key: 'default' } },
+                   stage: 'test' },
           spinach: { name: :spinach,
                      script: %w[spinach],
                      commands: 'spinach',
-                     stage: 'test',
-                     cache: { key: 'default' } })
+                     stage: 'test' })
       end
     end