Merge branch 'sh-squelch-null-store' into 'master'

Squelch output of ActiveSupport::Cache::NullStore in tests

See merge request gitlab-org/gitlab-ce!30055

spec/support/inspect_squelch.rb

+# This class can generate a lot of output if it fails,
+# so squelch the instance variable output.
+class ActiveSupport::Cache::NullStore
+  def inspect
+    "<#{self.class}>"
+  end
+end