Insecure content warning when running Recline under SSL

**Note**: This is not to be merged to master. The patch will get there as part of #1251 
The commit needs to be backported to 2.2.1 and 2.1.3

This is caused by requesting the http version of the MapQuest tiles and an image in the attribution in [1]

This has been fixed upstream in Recline (okfn/recline@efdf87db), we need to upgrade or patch with this change.

[1] https://github.com/ckan/ckan/blob/master/ckanext/reclinepreview/theme/public/vendor/recline/recline.js#L3628