Remove permission denied warning if unable write config to cache

[freax]

Remove warning "Warning: file_put_contents(data/cache/module-config-cache.application.config.cache.php): failed to open stream: Permission denied in ...".

[samsonasik]

I think it is hiding issue. I think we may have throw an Exception for this.

[weierophinney]

This is fixed with #39 and #53, which add the LOCK_EX flag as a third argument to file_put_contents(), ensuring the issue should not arise. (The issue typically occurs during race conditions from initial load.)

If you are seeing this for some other reason, please re-submit the pull request. However, as @samsonasik notes, you should raise an exception instead.