Cache routes only when caching enabled

[tsteur]

I pulled the latest changes from Git recently and whenever I open the changelog page locally, it would render the trac page. After a quick debug session noticed that the routes are cached despite caching disabled. I assume that this cache shouldn't be set unless caching is actually enabled. Might also give a performance update on production

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed

[michalkleiner]

There is already a PR for this with a discussion #842