Do not recreate expired files - overwrite existing files

[hermitdave]

Issue: #

PR Type

What kind of change does this PR introduce?

<- Bugfix >

What is the current behavior?

The cache instead of overwriting an existing file, recreates the file and then downloads the data. This would mean that in case of data / network failure, the cached copy has been destroyed and there is no newer copy to return to the consumer

What is the new behavior?

The cache does not overwrite existing file. Instead existing file if expired is passed to download method which overwrites it if successful.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added/updated which fit documentation template. (for bug fixes / features)
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information