Use DeepForge image on SciServer

[brollb]

The SciServer team has added a special DeepForge docker image to improve the performance when using SciServer Compute from DeepForge (thanks!). We should update DeepForge to use this image rather than configuring the "SciServer Essentials" image.

[umesh-timalsina]

This is great news. Hopefully, this will make our tests a lot stable as well as improve performance significantly.