Disable juint reports tmp

What does this MR do?

The junit reports are creating 90mb files inside of redis for gitlab-ce/ee project. There is an ongoing production incident gitlab-com/gl-infra/production#928 (closed) that is because of high CPU uitlaization on the redis nodes. GitLab-ce/ee are the highest consumers of memory becuase of these junit reports.

This is a bandage until we can scale redis properly.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team