index.html rendering thumbnail for scenes without proper bands

[jedsundwall]

Some scenes do not include all of the bands necessary to render a thumbnail, and their index pages look broken as a result.

Here are a few scenes with insufficient bands as an example:
https://s3-us-west-2.amazonaws.com/landsat-pds/L8/116/206/LT81162062015025LGN00/index.html
https://s3-us-west-2.amazonaws.com/landsat-pds/L8/116/202/LT81162022015025LGN00/index.html
https://s3-us-west-2.amazonaws.com/landsat-pds/L8/141/218/LT81412182015024LGN00/index.html

In instances where we do not have enough bands to produce a thumbnail, we should simply not insert a reference to a jpg. In the future, we may consider including messaging explaining that a limited set of bands is available for the scene.

[celoyd]

These can be identified by the scene ID. If it starts with LT, it has thermal bands only.