Multiple calls to get_plugins_supporting_mobile results in a bunch of "undefined variable $addons" spamming the page.

This is because under get_plugins_supporting_mobile there is a "require_once" which will require the mobile.php only once, therefore any subsequent call will not succeed as the file will not be included and $addons will not be there.

There are three possible solutions to this:

1. Change the require_once to a require
2. Change $pluginsinfo to a static variable and only build it once
3. Add MUC caching

Adding MUC caching seems appropriate as this API endpoint is called multiple times by admin settings pages as well as by the mobile app.