JSON resource lead to mapviewer and geoview resource previews

[jrods]

view_formats wasn't being reassigned to use the list from the config file which caused a string to string comparison rather than comparing a string to a list item.

This caused all JSON resources to have a mapview created automatically when geojson was specified in the config file.

Features:

• [ ] includes tests covering changes
• [ ] includes updated documentation
• [ ] includes user-visible changes
• [ ] includes API changes
• [x] includes bugfix for possible backport

Please [X] all the boxes above that apply

[amercader]

Nice catch, thanks @jrods