Do not show INTERNET callnumbers.

With the inclusion of SUL items we were getting a bunch of unnecessary location access panels for online-only materials as you can see in 8919378

![8919378-before](https://cloud.githubusercontent.com/assets/96776/3783197/3e493508-19aa-11e4-8998-5deaaab3fb73.png)

These have an item display field that looks like this

![8919378-item-display](https://cloud.githubusercontent.com/assets/96776/3783198/3e49dbfc-19aa-11e4-9864-39564dc42f91.png)


We can safely ignore this in the display.